Light-emitting diode (LED), LED package and apparatus including the same

ABSTRACT

A light-emitting diode (LED) package includes a light-emitting structure, an optical wavelength conversion layer on the light-emitting structure, and an optical filter layer on the optical wavelength conversion layer. The light-emitting structure includes a first-conductivity-type semiconductor layer, an active layer on the first-conductivity-type semiconductor layer, and a second-conductivity-type semiconductor layer on the active layer, and emits first light having a first peak wavelength. The optical wavelength conversion layer absorbs the first light emitted from the light-emitting structure and emits second light having a second peak wavelength different from the first peak wavelength. The optical filter layer reflects the first light emitted from the light-emitting structure and transmits the second light emitted from the optical wavelength conversion layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2015-0120547, filed on Aug. 26, 2015, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

The inventive concept relates to a light-emitting diode (LED), LEDpackage and an apparatus including the same, and more particularly, anLED package capable of emitting light of a second color by using an LEDthat emits light of a first color, and a three-color light-emittingapparatus and a display device including the LED.

LED packages may be used for small household appliances, interiorproducts, and display devices such as electronic boards. In order toenable the LED packages to be used for the display devices, the LEDpackages must be able to display three primary colors. However, in thecase of a package using LEDs of different colors, the configuration of adisplay device becomes complicated due to different operating voltagesand power consumption increases.

SUMMARY

The inventive concept provides a light-emitting diode (LED), an LEDpackage capable of emitting light of a second color by using an LED thatemits light of a first color.

In one embodiment, the inventive concept provides a three-colorlight-emitting apparatus and a display device including an LED.

According to an aspect of the inventive concept, there is provided anLED including: a light-emitting structure including afirst-conductivity-type semiconductor layer, an active layer on thefirst-conductivity-type semiconductor layer, and asecond-conductivity-type semiconductor layer on the active layer, andconfigured to emit first light having a first peak wavelength; anoptical wavelength conversion layer disposed on the light-emittingstructure and configured to absorb the first light emitted from thelight-emitting structure and emit second light having a second peakwavelength different from the first peak wavelength; and an opticalfilter layer disposed on the optical wavelength conversion layer andconfigured to reflect the first light emitted from the light-emittingstructure and transmit the second light emitted from the opticalwavelength conversion layer.

The optical wavelength conversion layer may be disposed between thelight-emitting structure and the optical filter layer.

The first peak wavelength may be included in a wavelength band of bluevisible light or a wavelength band of ultraviolet light.

The second peak wavelength may be included in a wavelength band of red,green, or yellow visible light.

The LED may further include a transparent substrate on the opticalfilter layer.

The LED may further include a transparent layer between the opticalwavelength conversion layer and the optical filter layer.

An upper surface of the second-conductivity-type semiconductor layercontacting the optical wavelength conversion layer may have unevenpatterns.

The optical filter layer may have a structure in which a firstdielectric film with a first refractive index and a first thickness anda second dielectric film with a second refractive index and a secondthickness are alternately stacked.

The first and second refractive indexes and the first and secondthicknesses may be designed such that each of a product of the firstrefractive index and the first thickness and a product of the secondrefractive index and the second thickness is substantially equal to ¼ ofthe first peak wavelength.

The optical filter layer may include a distributed Bragg reflector (DBR)configured to reflect light having the first peak wavelength.

The LED may further include a reflection layer disposed at a side of theoptical wavelength conversion layer and configured to reflect lightemitted from the optical wavelength conversion layer in a lateraldirection.

The LED may further include: a first electrode electrically connected tothe first-conductivity-type semiconductor layer; and a second electrodeelectrically connected to the second-conductivity-type semiconductorlayer.

The first and second electrodes may be disposed under thefirst-conductivity-type semiconductor layer, and the second electrodemay be electrically connected to the second-conductivity-typesemiconductor layer via a conductive via passing through thefirst-conductivity-type semiconductor layer and the active layer.

The first electrode may be disposed on a portion of thefirst-conductivity-type semiconductor layer, the active layer may bedisposed on another portion of the first-conductivity-type semiconductorlayer, and the second electrode may be disposed between thesecond-conductivity-type semiconductor layer and the optical wavelengthconversion layer.

The LED may further include a reflection layer disposed at a side of theactive layer and configured to reflect light emitted from the activelayer in a lateral direction.

The first electrode may be disposed under the first-conductivity-typesemiconductor layer and include an extension portion extending in alateral direction and exposed to the outside, and the second electrodemay be disposed under the first electrode and be electrically connectedto the second-conductivity-type semiconductor layer via a conductive viapassing through the first electrode, the first-conductivity-typesemiconductor layer, and the active layer.

According to another aspect of the inventive concept, there is provideda three-color light-emitting apparatus including: first to thirdlight-emitting structures each including a first-conductivity-typesemiconductor layer, an active layer, and a second-conductivity-typesemiconductor layer and configured to emit first light having a firstpeak wavelength; a first optical wavelength conversion layer disposed onthe first light-emitting structure and configured to absorb the firstlight emitted from the first light-emitting structure and emit secondlight having a second peak wavelength different from the first peakwavelength; a second optical wavelength conversion layer disposed on thesecond light-emitting structure and configured to absorb the first lightemitted from the second light-emitting structure and emit third lighthaving a third peak wavelength different from the first and second peakwavelengths; and first and second optical filter layers respectivelydisposed on the first and second optical wavelength conversion layersand configured to reflect the first light emitted from the first andsecond light-emitting structures.

The first peak wavelength may be included in a wavelength band of bluevisible light, the second peak wavelength may be included in awavelength band of red visible light, and the third peak wavelength maybe included in a wavelength band of green or yellow visible light.

Each of the first and second optical filter layers may have a structurein which a first dielectric film with a first refractive index and asecond dielectric film with a second refractive index are alternatelystacked.

A planar area of the third light-emitting structure among the first tothird light-emitting structures may be smallest.

According to another aspect of the inventive concept, there is provideda display device including: a plurality of pixels each including atleast a first subpixel with a first LED, and a second subpixel with asecond LED, wherein the first LED includes: a first light-emittingstructure including a first-conductivity-type semiconductor layer, anactive layer, and a second-conductivity-type semiconductor layer andconfigured to emit first light having a first peak wavelength; a firstoptical wavelength conversion layer disposed on the first light-emittingstructure and configured to absorb the first light emitted from thefirst light-emitting structure and emit second light having a secondpeak wavelength different from the first peak wavelength; and a firstoptical filter layer disposed on the first optical wavelength conversionlayer and configured to reflect the first light emitted from the firstlight-emitting structure and transmit the second light emitted from thefirst optical wavelength conversion layer.

The second LED may include: a second light-emitting structure includingthe first-conductivity-type semiconductor layer, the active layer, andthe second-conductivity-type semiconductor layer and configured to emitthe first light having the first peak wavelength; a second opticalwavelength conversion layer disposed on the second light-emittingstructure and configured to absorb the first light emitted from thesecond light-emitting structure and emit third light having a third peakwavelength different from the first and second peak wavelengths; and asecond optical filter layer disposed on the second optical wavelengthconversion layer and configured to reflect the first light emitted fromthe second light-emitting structure and transmit the third light emittedfrom the second optical wavelength conversion layer.

Each of the pixels may further include a third subpixel having a thirdlight-emitting structure including the first-conductivity-typesemiconductor layer, the active layer, and the second-conductivity-typesemiconductor layer and configured to emit the first light having thefirst peak wavelength.

The first LED may emit red light, the second LED emits green light, andthe third LED emits blue light.

A planar area of the third subpixel among the first to third subpixelsmay be smallest.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the inventive concept will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a part of a light-emitting diode(LED) package according to an exemplary embodiment of the inventiveconcept;

FIG. 2 is a cross-sectional view of a part of an LED according toanother exemplary embodiment of the inventive concept;

FIG. 3 is a cross-sectional view of a part of an LED according toanother exemplary embodiment of the inventive concept;

FIG. 4 is a cross-sectional view of a part of an LED according toanother exemplary embodiment of the inventive concept;

FIG. 5 is a cross-sectional view of a part of an LED according toanother exemplary embodiment of the inventive concept;

FIG. 6 is a cross-sectional view of a part of an LED according toanother exemplary embodiment of the inventive concept;

FIG. 7 is a cross-sectional view of a part of an LED according toanother exemplary embodiment of the inventive concept;

FIG. 8 is a cross-sectional view of a part of an LED according toanother exemplary embodiment of the inventive concept;

FIG. 9 is a cross-sectional view of a part of an LED according toanother exemplary embodiment of the inventive concept;

FIG. 10 is a cross-sectional view of an LED package according to anotherexemplary embodiment of the inventive concept;

FIG. 11 is a cross-sectional view of an LED package according to anotherexemplary embodiment of the inventive concept;

FIG. 12 is a cross-sectional view of an LED package according to anotherexemplary embodiment of the inventive concept;

FIGS. 13A to 13K are cross-sectional views for describing a method ofmanufacturing the LED package of FIG. 12, according to an exemplaryembodiment of the inventive concept;

FIG. 14 is a block diagram of a three-color light-emitting apparatususing LEDs or LED packages according to various exemplary embodiments ofthe inventive concept;

FIG. 15 is a cross-sectional view of a structure of a quantum dot;

FIG. 16 is a block diagram of a display device using LEDs or LEDpackages according to various exemplary embodiments of the inventiveconcept;

FIGS. 17A and 17B are block diagrams of pixels of the display deviceillustrated in FIG. 16; and

FIG. 18 is a circuit diagram of a subpixel illustrated in FIG. 17A.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, exemplary embodiments of the inventive concept will bedescribed with reference to the accompanying drawings. The inventiveconcept may, however, be embodied in many different forms and should notbe construed as being limited to the exemplary embodiments set forthherein; rather, these exemplary embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey theinventive concept to those of ordinary skill in the art. It should beunderstood, however, that there is no intent to limit the inventiveconcept to the particular forms disclosed, but on the contrary, theinventive concept is to cover all modifications, equivalents, andalternatives falling within the spirit and scope of the inventiveconcept. In the drawings, the dimensions of structures are exaggeratedfor clarity of the inventive concept.

Hereinafter, exemplary embodiments of the inventive concept will bedescribed with reference to the accompanying drawings. In theaccompanying drawings, the modifications of the illustrated shapes maybe expected according to manufacturing technologies and/or tolerance.Therefore, the exemplary embodiments should not be construed as beinglimited to specific shapes of the illustrated regions. The shapes may bechanged during the manufacturing processes. The following exemplaryembodiments may be combined.

FIG. 1 is a cross-sectional view of a part of a light-emitting diode(LED) 100 according to an exemplary embodiment of the inventive concept.

Referring to FIG. 1, the LED 100 may include a light-emitting structure140, an optical wavelength conversion layer 150, and an optical filterlayer 160.

The light-emitting structure 140 may include a first-conductivity-typesemiconductor layer 110, an active layer 120, and asecond-conductivity-type semiconductor layer 130, which are sequentiallystacked.

The first-conductivity-type semiconductor layer 110 may be an n-typenitride semiconductor having a composition of In_(x)Al_(y)Ga_(1-x-y)N(0≦x<1, 0≦y<1, 0≦x+y<1), and an n-type impurity may be silicon (Si). Forexample, the first-conductivity-type semiconductor layer 110 may includen-type GaN.

According to an exemplary embodiment, the first-conductivity-typesemiconductor layer 110 may include a first-conductivity-typesemiconductor contact layer 111 and a current diffusion layer 112.

An impurity concentration of the first-conductivity-type semiconductorcontact layer 111 may be in the range of about 2×10¹⁸ cm⁻³ to about9×10¹⁹ cm⁻³. The first-conductivity-type semiconductor contact layer 111may have a thickness of about 1 μm to about 5 μm.

The current diffusion layer 112 may have a structure in which aplurality of InAl_(y)Ga_((1-x-y))N layers (0≦x, y≦1, 0≦x+y≦1) havingdifferent compositions or different impurity content are repeatedlystacked. For example, the current diffusion layer 112 may have athickness of about 1 nm to about 500 nm and may be an n-typesuperlattice layer in which two or more different layers having acomposition of Al_(x)In_(y)Ga_(z)N (0≦x,y,z≦1, except for x=y=z=0) likean n-type GaN layer are repeatedly stacked. An impurity concentration ofthe current diffusion layer 112 may be in the range of about 2×10¹⁸ cm⁻³to about 9×10¹⁹ cm⁻³. If necessary, the current diffusion layer 112 mayfurther include an insulating material layer.

The second-conductivity-type semiconductor layer 130 may be a nitridesemiconductor satisfying p-type In_(x)Al_(y)Ga_(1-x-y)N (0≦x<1, 0≦y<1,0≦x+y<1), and a p-type impurity may be magnesium (Mg). Thesecond-conductivity-type semiconductor layer 130 may have a single-layerstructure, but may also have a multilayer structure with differentcompositions. The second-conductivity-type semiconductor layer 130 mayinclude an electron blocking layer (EBL) 131, a low-concentration p-typeGaN layer 132, and a high-concentration p-type GaN layer 133 serving asa contact layer.

For example, the electron blocking layer 131 may have a thickness ofabout 5 nm to about 100 nm and may have a structure in whichIn_(x)Al_(y)Ga_((1-x-y))N layers having different compositions arestacked, or may be a single layer including Al_(y)Ga_((1-y))N. An energyband gap (Eg) of the electron blocking layer 131 may decrease as thedistance from the active layer 120 increases. For example, aluminium(Al) content of the electron blocking layer 131 may decrease as thedistance from the active layer 120 increases.

The active layer 120 may have a multi quantum well (MQW) structure inwhich a quantum well layer and a quantum barrier layer are alternatelystacked. For example, the quantum well layer and the quantum barrierlayer may include In_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1) havingdifferent compositions. According to an exemplary embodiment, thequantum well layer may include In_(x)Ga_(1-x)N (0<x≦1) and the quantumbarrier layer may include GaN or AlGaN. Each of the quantum well layerand the quantum barrier layer may have a thickness of about 1 nm toabout 50 nm. The active layer 120 is not limited to the MQW structureand may have a single quantum well (SQW) structure.

The LED 100 may further include a first electrode (not illustrated)electrically connected to the first-conductivity-type semiconductorlayer 110, and a second electrode (not illustrated) electricallyconnected to the second-conductivity-type semiconductor layer 130. Thelight-emitting structure 140, to which the first and second electrodesare connected, may be referred to as an LED or a semiconductor LED. Thefirst and second electrodes may be disposed at various positions andhave various shapes, depending on the configuration of the LED.

The light-emitting structure 140 may emit first light having a firstpeak wavelength. The first peak wavelength may be included in awavelength band of a first color of visible light or may be included ina wavelength band of ultraviolet light. As one example, the first colormay be a blue color. As another example, the first color may be a redcolor, a green color, or a yellow color.

The optical wavelength conversion layer 150 may be disposed on thelight-emitting structure 140. The optical wavelength conversion layer150 may be disposed between the light-emitting structure 140 and theoptical filter layer 160.

The optical wavelength conversion layer 150 may absorb the first lighthaving the first peak wavelength, which is emitted from thelight-emitting structure 140, and emit second light having a second peakwavelength. The second peak wavelength may be different from the firstpeak wavelength and the first color may be different from the secondcolor. The second peak wavelength may be included in a wavelength bandof the second color of visible light. The second color may be one of ared color, a green color, and a yellow color. According to anotherexemplary embodiment, when the color of the first light emitted from thelight-emitting structure 140 is one of a red color, a green color, and ayellow color, the second color of the light emitted from the opticalwavelength conversion layer 150 may be a blue color.

Various materials, such as phosphors and/or quantum dots, may be used asa wavelength conversion material for converting the wavelength of thefirst light emitted from the light-emitting structure 140.

The phosphors used for the optical wavelength conversion layer 150 mayhave the following empirical formulas and colors.

Oxide-based: yellow color and green color Y₃Al₅O₁₂:Ce, Tb₃Al₅O₁₂:Ce,Lu₃Al₅O₁₂:Ce

Silicate-based: yellow color and green color (Ba,Sr)₂SiO₄:Eu, yellowcolor and orange color (Ba,Sr)₃SiO₅:Ce

Nitride-based: green color β-SiAlON:Eu, yellow color La₃Si₆O₁₁:Ce,orange color α-SiAlON:Eu, red color CaAlSiN₃:Eu, Sr₂Si₅N₈:Eu,SrSiAl₄N₇:Eu, SrLiAl₃N₄:Eu,Ln_(4-x)(Eu_(z)M_(1-z))_(x)Si_(12-y)Al_(y)O_(3+x+y)N_(18-x-y) (0.5≦x≦3,0<z<0.3, 0<y≦4)

Herein, Ln may be at least one of group IIIa elements or rare-earthelements, and M may be at least one of calcium (Ca), barium (Ba),strontium (Sr), or magnesium (Mg).

Fluoride-based: KSF-based red color K₂SiF₆:Mn₄ ⁺, K₂TiF₆:Mn₄ ⁺,NaYF₄:Mn₄ ⁺, NaGdF₄:Mn₄ ⁺, K₃SiF₇:Mn₄ ⁺

The composition of the phosphor basically needs to conform withstoichiometry, and the respective elements may be substituted by otherelements included in the respective groups of the periodic table. Forexample, strontium (Sr) may be substituted by at least one of barium(Ba), calcium (Ca), or magnesium (Mg) of alkaline-earth group II, and Ymay be substituted by at least one of terbium (Tb), lutetium (Lu),scandium (Sc), and gadolinium (Gd). In addition, europium (Eu), which isan activator, may be substituted by at least one of cerium (Ce), terbium(Tb), praseodymium (Pr), erbium (Er), or ytterbium (Yb) according to adesired energy level. The activator may be applied solely or asub-activator may be additionally applied to modify the characteristicsof the phosphor.

In particular, in order to improve the reliability at high-temperatureand high-humidity conditions, the fluoride-based red phosphor may becoated with an Mn-free fluoride material or may further include anorganic coating on the surface of the phosphor or the coated surface ofthe Mn-free fluoride material. In the case of the fluoride-based redphosphor, a narrow full width at half maximum (FWHM) of about 40 nm orless unlike other phosphors can be implemented. Thus, the fluoride-basedred phosphor may be applied to a high-resolution TV such as anultra-high-definition (UHD) TV.

Table 1 below shows phosphors usable as the wavelength conversionmaterials according to applications when the peak wavelength of thelight emitted from the light-emitting structure 140 is within awavelength band of blue visible light (about 440 nm to about 460) or awavelength ban of ultraviolet light (about 380 nm to about 440 nm).

TABLE 1 Usage Phosphor LED TV BLU β-SiAlON:Eu2+ (Ca, Sr)AlSiN3:Eu2+La₃Si₆N₁₁:Ce3+ K₂SiF₆:Mn4+ SrLiAl₃N₄:EuLn_(4−x)(Eu_(z)M_(1−z))_(x)Si_(12−y)Al_(y)O_(3+x+y)N_(18−x−y) (0.5 ≦ x ≦3, 0 < z < 0.3, 0 < y ≦ 4) K2TiF6:Mn4+ NaYF4:Mn4+ NaGdF4:Mn4+Illumination Lu₃Al₅O₁₂:Ce3+ Ca-α-SiAlON:Eu2+ La₃Si₆N₁₁:Ce3+ (Ca,Sr)AlSiN₃:Eu2+ Y₃Al₅O₁₂:Ce3+ K₂SiF₆:Mn4+ SrLiAl3N4:EuLn_(4−x)(Eu_(z)M_(1−z))_(x)Si_(12−y)Al_(y)O_(3+x+y)N_(18−x−y) (0.5 ≦ x ≦3, 0 < z < 0.3, 0 < y ≦ 4) K₂TiF₆:Mn4+ NaYF4:Mn4+ NaGdF4:Mn4+ Side ViewLu₃Al₅O₁₂:Ce3+ (Mobile, Note PC) Ca-α-SiAlON:Eu2+ La₃Si₆N₁₁:Ce3+ (Ca,Sr)AlSiN₃:Eu2+ Y₃Al₅O₁₂:Ce3+ (Sr, Ba, Ca, Mg)2SiO4:Eu2+ K₂SiF₆:Mn4+SrLiAl3N4:EuLn_(4−x)(Eu_(z)M_(1−z))_(x)Si_(12−y)Al_(y)O_(3+x+y)N_(18−x−y) (0.5 ≦ x ≦3, 0 < z < 0.3, 0 < y ≦ 4) K2TiF6:Mn4+ NaYF4:Mn4+ NaGdF4:Mn4+ ElectricalLu₃Al₅O₁₂:Ce3+ Component Ca-α-SiAlON:Eu2+ (Head Lamp, etc.)La₃Si₆N₁₁:Ce3+ (Ca, Sr)AlSiN₃:Eu2+ Y₃Al₅O₁₂:Ce3+ K₂SiF₆:Mn4+SrLiAl3N4:EuLn_(4−x)(Eu_(z)M_(1−z))_(x)Si_(12−y)Al_(y)O_(3+x+y)N_(18−x−y) (0.5 ≦ x ≦3, 0 < z < 0.3, 0 < y ≦ 4) K2TiF6:Mn4+ NaYF4:Mn4+ NaGdF4:Mn4+

The wavelength conversion layer 150 may include a quantum dot (QD) asthe wavelength conversion material, instead of the phosphor or incombination with the phosphor.

FIG. 15 is a cross-sectional view of a structure of a QD. Referring toFIG. 15, the QD may have a core-shell structure using group III-V orII-VI compound semiconductors. For example, the QD may have a core suchas CdSe or InP and a shell such as ZnS or ZnSe. The core may have adiameter of about 1 nm to about 30 nm, or about 3 nm to about 10 nm. Theshell may have a thickness of about 0.1 nm to about 20 nm, or about 0.5nm to about 2 nm In addition, the QD may include a ligand forstabilizing the core and the shell.

The QD may implement various colors depending on its size. Inparticular, when the QD is used as a phosphor substitute, the QD may beused as a wavelength conversion material to emit red light or greenlight. If the QD is used as the wavelength conversion material, a narrowFWHM of about 35 nm may be achieved.

Referring to FIG. 1 again, the optical filter layer 160 may be disposedon the optical wavelength conversion layer 150. The optical filter layer160 may reflect the first light having the first peak wavelength emittedfrom the light-emitting structure 140, and transmit the second lighthaving the second peak wavelength emitted from the optical wavelengthconversion layer 150. Portion A of FIG. 1 illustrates an enlargedcross-section of the optical filter layer 160.

The optical filter layer 160 may have a multilayer reflection structurein which a plurality of dielectric films having different refractiveindexes are alternately stacked. For example, the optical filter layer160 may have a multilayer reflection structure in which a firstdielectric film 161 having a first refractive index n1 and a firstthickness d1 and a second dielectric film 162 having a second refractiveindex n2 and a second thickness d2 are alternately and repeatedlystacked. According to an exemplary embodiment, the optical filter layer160 may be a distributed Bragg reflector (DBR) configured to reflect thefirst light having the first peak wavelength emitted from thelight-emitting structure 140.

The multilayer reflection structure may have a structure in which aplurality of dielectric films (e.g., 161 and 162) having differentrefractive indexes are alternately stacked twice to hundred times. Forexample, in order to form the optical filter layer 160 having themultilayer reflection structure, the first and second dielectric films161 and 162 may be alternately stacked three times to seventy times, orfour times to fifty times.

Each of the first and second dielectric films 161 and 162 in themultilayer reflection structure may include oxide or nitride (e.g.,SiO₂, SiN, SiO_(x)N_(y), TiO₂, Nb₂O₅, Si₃N₄, Al₂O₃, TiN, MN, ZrO₂,TiAlN, TiSiN, etc.), or any mixtures thereof. For example, the firstdielectric film 161 may include silicon oxide (SiO₂), and the seconddielectric film 162 may include titanium oxide (TiO₂) or niobium oxide(Nb₂O₅).

A refractive index of each of the first and second dielectric films 161and 162 may be in the range of about 1.4 to about 3.0. A dielectric filmcontacting the optical wavelength conversion layer 150 may be selectedas a dielectric film having a difference within 1.6 in a refractiveindex from the optical wavelength conversion layer 150 among the firstand second dielectric films 161 and 162. In addition, a dielectric filmdisposed in the uppermost portion of the optical filter layer 160 may beselected as a dielectric film having a low refractive index among thefirst and second dielectric films 161 and 162.

When the first peak wavelength of the first light generated by theactive layer 120 of the light-emitting structure 140 is λ1 and therefractive indexes of the first and second dielectric films 161 and 162are n1 and n2, respectively, the thicknesses of the first and seconddielectric films 161 and 162 are λ1/4n1 and λ2/4n2, respectively. Thatis, the product (n1×d1) of the first refractive index n1 and the firstthickness d1 of the first dielectric film 161 may be equal to ¼ of thefirst peak wavelength (2J), i.e., (λ1)/4. The product (n2×d2) of thesecond refractive index n2 and the second thickness d2 of the seconddielectric film 162 may be equal to ¼ of the first peak wavelength (λ1),i.e., (λ1)/4. The thicknesses d1 and d2 of the first and seconddielectric films 161 and 162 may be in the range of about 300 □ to about900 □. The first refractive index n1 and the first thickness d1 of thefirst dielectric film 161 and the second refractive index n2 and thesecond thickness d2 of the second dielectric film 162 may beappropriately selected and the number of stacks of the first and seconddielectric films 161 and 162 may be selected, so that the multilayerreflection structure of the optical filter layer 160 has a highreflectivity of about 95% or more with respect to the first peakwavelength (2J) of the first light generated by the active layer 120.

The optical filter layer 160 may selectively reflect only the firstlight having the first peak wavelength, emitted from the light-emittingstructure 140, and transmit light having the other wavelengths. Forexample, the optical filter layer 160 may transmit the second lighthaving the second peak wavelength emitted from the optical wavelengthconversion layer 150. Therefore, the optical filter layer 160 mayfunction as a band-stop optical filter that reflects only the firstlight having the first peak wavelength. According to another exemplaryembodiment, the optical filter layer 160 may function as a band-passoptical filter that transmits only the second light having the secondpeak wavelength. According to another exemplary embodiment, when thefirst peak wavelength is shorter than the second peak wavelength, theoptical filter layer 160 may function as a low-pass optical filter thatblocks the first light having the first peak wavelength and transmitsthe second light having the second peak wavelength.

Although not illustrated in FIG. 1, a reflection layer, from which thefirst light generated by the active layer 120 is reflected, may bedisposed under the first-conductivity-type semiconductor layer 110.

FIG. 2 is a cross-sectional view of a part of an LED 100 a according toanother exemplary embodiment of the inventive concept.

Referring to FIG. 2, the LED 100 a may include a light-emittingstructure 140, an optical wavelength conversion layer 150, an opticalfilter layer 160, and a transparent substrate 170 a. The light-emittingstructure 140 may include a first-conductivity-type semiconductor layer110, an active layer 120, and a second-conductivity-type semiconductorlayer 130, which are sequentially stacked. The light-emitting structure140, the optical wavelength conversion layer 150, and the optical filterlayer 160 of the LED 100 a illustrated in FIG. 2 respectively correspondto the light-emitting structure 140, the optical wavelength conversionlayer 150, and the optical filter layer 160 of the LED 100 illustratedin FIG. 1, and redundant descriptions thereof will be omitted for thesake of simplicity.

The transparent substrate 170 a may be so transparent as to transmitsecond light having a second peak wavelength which is generated from theoptical wavelength conversion layer 150 and passes through the opticalfilter layer 160. The transparent substrate 170 a may include glass,silicon, or polymer.

A refractive index of the transparent substrate 170 a may be lower thanrefractive indexes of first and second dielectric films 161 and 162 ofthe optical filter layer 160. A dielectric film disposed in theuppermost portion of the optical filter layer 160 may be selected as adielectric film having a difference within 1.6 in a refractive indexfrom the transparent substrate 170 a among the first and seconddielectric films 161 and 162.

The optical filter layer 160 may be disposed on the transparentsubstrate 170 a. The transparent substrate 170 a may support the opticalfilter layer 160. The optical filter layer 160 disposed on thetransparent substrate 170 a may be fixed on the optical wavelengthconversion layer 150. Before the optical wavelength conversion layer 150is completely cured, the transparent substrate 170 a on which theoptical filter layer 160 is formed is turned over and the opticalwavelength conversion layer 150 is pressed against the optical filterlayer 160. Then, the optical wavelength conversion layer 150 is cured.In this manner, the optical filter layer 160 may be bonded to theoptical wavelength conversion layer 150. The optical filter layer 160may be bonded to the optical wavelength conversion layer 150 by using anadhesive.

FIG. 3 is a cross-sectional view of a part of an LED 100 b according toanother exemplary embodiment of the inventive concept.

Referring to FIG. 3, the LED 100 b may include a light-emittingstructure 140, an optical wavelength conversion layer 150, a transparentlayer 170 b, and an optical filter layer 160. The light-emittingstructure 140 may include a first-conductivity-type semiconductor layer110, an active layer 120, and a second-conductivity-type semiconductorlayer 130, which are sequentially stacked. The light-emitting structure140, the optical wavelength conversion layer 150, and the optical filterlayer 160 of the LED 100 b illustrated in FIG. 3 respectively correspondto the light-emitting structure 140, the optical wavelength conversionlayer 150, and the optical filter layer 160 of the LED 100 illustratedin FIG. 1, and redundant descriptions thereof will be omitted.

The transparent layer 170 b may be transparent so that second lighthaving a second peak wavelength, which is generated from the opticalwavelength conversion layer 150, travels toward the optical filter layer160. The transparent layer 170 b may include glass, silicon, or polymer.The transparent layer 170 b may be substantially the same as thetransparent substrate 170 a illustrated in FIG. 2, except for thepositions of the transparent layer 170 b and the transparent substrate170 a.

The transparent substrate 170 a may be made of a material having arefractive index in a range between a refractive index of the opticalwavelength conversion layer 150 and a refractive index of the first orsecond dielectric film 161 or 162. A dielectric film contacting thetransparent layer 170 b may be selected as a dielectric film having asmall difference in a refractive index from the transparent layer 170 bamong the first and second dielectric films 161 and 162.

The optical filter layer 160 may be disposed on the transparent layer170 b such as a transparent substrate. The transparent layer 170 bdisposed on the optical filter layer 160 may be fixed on the opticalwavelength conversion layer 150. Before the optical wavelengthconversion layer 150 is completely cured, the transparent layer 170 b onwhich the optical filter layer 160 is formed is pressed against theoptical filter layer 160, and the optical wavelength conversion layer150 is cured. In this manner, the transparent layer 170 b may be bondedon the optical wavelength conversion layer 150. The transparent layer170 b on which the optical filter layer 160 is formed may be bonded tothe optical wavelength conversion layer 150 by using an adhesive.

FIG. 4 is a cross-sectional view of a part of an LED 100 c according toanother exemplary embodiment of the inventive concept.

Referring to FIG. 4, the LED 100 c may include a light-emittingstructure 140, an optical wavelength conversion layer 150, and anoptical filter layer 160. The light-emitting structure 140 may include afirst-conductivity-type semiconductor layer 110, an active layer 120,and a second-conductivity-type semiconductor layer 130, which aresequentially stacked. The LED 100 c may be substantially identical tothe LED 100 illustrated in FIG. 1, except that uneven patterns P areformed on the upper surface of the light-emitting structure 140 suchthat the interface between the light-emitting structure and the opticalwavelength conversion layer 150 is non-planar. The light-emittingstructure 140, the optical wavelength conversion layer 150, and theoptical filter layer 160 of the LED 100 c illustrated in FIG. 4respectively correspond to the light-emitting structure 140, the opticalwavelength conversion layer 150, and the optical filter layer 160 of theLED 100 illustrated in FIG. 1, and redundant descriptions thereof willbe omitted. The stacking order of the first-conductivity-typesemiconductor layer 110, the active layer 120, and thesecond-conductivity-type semiconductor layer 130 in FIG. 4 is differentfrom the stacking order of the first-conductivity-type semiconductorlayer 110, the active layer 120, and the second-conductivity-typesemiconductor layer 130 in FIG. 1. Specifically, thefirst-conductivity-type semiconductor layer 110 may be disposed on theactive layer 120, and the active layer 120 may be disposed on thesecond-conductivity-type semiconductor layer 130.

As illustrated in FIG. 4, the uneven patterns P may be formed on theupper surface of the light-emitting structure 140, that is, the uppersurface of the first-conductivity-type semiconductor layer 110. Theuneven patterns P may increase the light extraction efficiency of theLED 100 c.

The uneven patterns P may be formed on the upper surface of thefirst-conductivity-type semiconductor layer 110 by sequentially formingthe first-conductivity-type semiconductor layer 110, the active layer120, and the second-conductivity-type semiconductor layer 130 on asubstrate having an uneven surface, turning over the substrate, andremoving the substrate. The uneven patterns P may improve the singlecrystal quality of the second-conductivity-type semiconductor layer 130.

FIG. 5 is a cross-sectional view of a part of an LED 100 d according toanother exemplary embodiment of the inventive concept.

Referring to FIG. 5, the LED 100 d may include a light-emittingstructure 140, an optical wavelength conversion layer 150, a reflectionlayer 180, and an optical filter layer 160. The light-emitting structure140 may include a first-conductivity-type semiconductor layer 110, anactive layer 120, and a second-conductivity-type semiconductor layer130, which are sequentially stacked.

The LED 100 d may be substantially identical to the LED 100 illustratedin FIG. 1, except that the reflection layer 180 is further included. Thelight-emitting structure 140, the optical wavelength conversion layer150, and the optical filter layer 160 of the LED 100 d illustrated inFIG. 5 respectively correspond to the light-emitting structure 140, theoptical wavelength conversion layer 150, and the optical filter layer160 of the LED 100 illustrated in FIG. 1, and redundant descriptionsthereof will be omitted.

The reflection layer 180 may be disposed at a side, for example, alateral side, of the optical wavelength conversion layer 150 and preventlateral emission of first light that is not completely absorbed in theoptical wavelength conversion layer 150. The reflection layer 180 mayreflect the first light, which is generated from the light-emittingstructure 140 and is emitted in a lateral direction through the opticalwavelength conversion layer 150, toward the inside of the opticalwavelength conversion layer 150. The reflection layer 180 may include areflective material, such as TiO₂ or Al₂O₃. According to anotherexemplary embodiment, the reflection layer 180 may have a multilayerreflection structure in which a plurality of dielectric films havingdifferent refractive indexes are alternately stacked. According toanother exemplary embodiment, the reflection layer 180 may have a lightreflection structure formed by dispersing a light reflective filler in alight transmissive material. Although not illustrated in FIG. 5, thereflection layer 180 may extend downward to cover the side of thelight-emitting structure 140. The reflection layer 180, which extends tothe side of the light-emitting structure 140, may prevent externalemission of the first light emitted from the active layer 120. Accordingto another exemplary embodiment, an additional reflection layer may bedisposed at the side of the light-emitting structure 140, for example,at the side of the active layer 120. Since the reflection layer 180 isdisposed at the sides of the light-emitting structure 140 and theoptical wavelength conversion layer 150, the first light generated bythe light-emitting structure 140 is not emitted to the outside of theLED 100 d, and only the second light having the second peak wavelength,which is generated by the optical wavelength conversion layer 150, isemitted to the outside of the LED 100 d. Therefore, the LED 100 d mayemit only a high-purity light of a second color.

FIG. 6 is a cross-sectional view of a part of an LED 200 according toanother exemplary embodiment of the inventive concept.

Referring to FIG. 6, the LED 200 may include a light-emitting structure240, an optical wavelength conversion layer 250, and an optical filterlayer 260. The light-emitting structure 240 may include afirst-conductivity-type semiconductor layer 210, an active layer 220,and a second-conductivity-type semiconductor layer 230, which aresequentially stacked. The light-emitting structure 240, the opticalwavelength conversion layer 250, and the optical filter layer 260 of theLED 200 illustrated in FIG. 6 respectively correspond to thelight-emitting structure 140, the optical wavelength conversion layer150, and the optical filter layer 160 of the LED 100 illustrated in FIG.1, and redundant descriptions thereof will not be repeated. The stackingorder of the light-emitting structure 240 illustrated in FIG. 6 issubstantially identical to the stacking order of the light-emittingstructure 140 illustrated in FIG. 4. That is, thefirst-conductivity-type semiconductor layer 210 may be disposed on theactive layer 220, and the active layer 220 may be disposed on thesecond-conductivity-type semiconductor layer 230. In addition, similarto the LED 100 c of FIG. 4, the first-conductivity-type semiconductorlayer 210 may have an uneven upper surface so as to improve the lightextraction efficiency of the LED 200 and the single crystal quality ofthe light-emitting structure 240.

The LED 200 may further include a transparent substrate 270 on theoptical filter layer 260, and a reflection layer 280 that covers a sideof the optical wavelength conversion layer 250. As illustrated in FIG.6, the reflection layer 280 may cover a side of at least a portion ofthe first-conductivity-type semiconductor layer 210. The transparentsubstrate 270 and the reflection layer 280 respectively correspond tothe transparent substrate 170 a of the LED 100 b illustrated in FIG. 2and the reflection layer 180 of the LED 100 d illustrated in FIG. 5, andredundant descriptions thereof will be omitted. According to anotherexemplary embodiment, the LED 200 may include a transparent layerbetween the optical wavelength conversion layer 250 and the opticalfilter layer 260, instead of the transparent substrate 270.

The LED 200 may further include a first electrode 201 and a secondelectrode 202. The first electrode 201 and the second electrode 202 maybe electrically connected to the first-conductivity-type semiconductorlayer 210 and the second-conductivity-type semiconductor layer 230,respectively.

The first electrode 201 may include one or more conductive vias 201 athat pass through the second-conductivity-type semiconductor layer 230and the active layer 220 and are connected to thefirst-conductivity-type semiconductor layer 210, and a first electrodepad 201 b connected to the conductive via 201 a. The conductive via 201a may be surrounded by an insulating layer 205 and be electricallyisolated from the active layer 210 and the second-conductivity-typesemiconductor layer 230. The conductive via 201 a may be disposed withina contact hole formed by etching the light-emitting structure 240. Inorder to reduce the contact resistance between the conductive via 201 aand the first-conductivity-type semiconductor layer 210, the number,shape, and pitch of the conductive vias 201 a or the contact areatherebetween may be appropriately selected. In addition, since theconductive via 201 a is arranged to form a row and a column in thelight-emitting structure 210, a current flow between the first electrode201 and the second electrode 202 can be improved. The second electrode202 may include an ohmic contact layer 202 a and a second electrode pad202 b on the second-conductivity-type semiconductor layer 230.

The conductive via 201 a and the ohmic contact layer 202 b may have asingle-layer or multilayer structure of a conductive material havingohmic characteristics with the first-conductivity-type semiconductorlayer 210 and the second-conductivity-type semiconductor layer 230. Forexample, the conductive via 201 a and the ohmic contact layer 202 b maybe formed by depositing or sputtering at least one of conductivematerials, such as Ag, Al, Ni, Cr, or transparent conductive oxide(TCO).

The first and second electrode pads 201 b and 202 b may be respectivelyconnected to the conductive via 201 a and the ohmic contact layer 202 band function as external terminals of the light-emitting structure 240.For example, the first and second electrode pads 201 b and 202 b mayinclude Au, Ag, Al, Ti, W, Cu, Sn, Ni, Pt, Cr, NiSn, TiW, AuSn, oreutectic metal thereof. The first and second electrodes 201 and 202 maybe disposed in the same direction. For example, the first and secondelectrodes 201 and 202 may be mounted on a lead frame in a so-calledflip-chip manner.

The first and second electrodes 201 and 202 may be electricallyseparated from each other by the insulating layer 205. Any suitablematerials may be used for the insulating layer 205 as long as thematerials have electrically insulating characteristics. Although anymaterials having electrically insulating characteristics may be used forthe insulating layer 205, a material having a low light absorption ratecan be used. For example, the insulating layer 205 may include siliconoxide or silicon nitride, such as SiO₂, SiO_(x)N_(y), or Si_(x)N_(y).According to another exemplary embodiment, the insulating layer 205 mayhave a light reflection structure formed by dispersing a lightreflective filler in a light transmissive material. According to anotherexemplary embodiment, the insulating layer 205 may have a multilayerreflection structure in which a plurality of insulating films havingdifferent refractive indexes are alternately stacked. For example, theinsulating layer 205 may be a DBR in which a first insulating filmhaving a first refractive index and a second insulating film having asecond refractive index are alternately stacked.

The multilayer reflection structure may be formed by repeatedly stackinga plurality of insulating films having different refractive indexestwice or more. For example, the plurality of insulating films havingdifferent refractive indexes may be repeatedly stacked twice to hundredtimes, three times to seventy times, or four times to fifty times. Eachof the insulating films having the multilayer reflection structure mayinclude oxide or nitride (e.g., SiO₂, SiN, SiO_(x)N_(y), TiO₂, Si₃N₄,Al₂O₃, TiN, MN, ZrO₂, TiAlN, TiSiN, etc.), or any mixtures thereof. Forexample, when the first peak wavelength of the first light generated bythe active layer 220 is λ1 and the refractive indexes of the first andsecond insulating films are n1 and n2, respectively, the first andsecond insulating films may be formed to have a thickness of λ1/4n1 andλ1/4n2, respectively, For example, the insulating films included in theinsulating layer 205 may have a thickness of about 300 Å and about 900Å, respectively. The refractive indexes and thicknesses of theinsulating films included in the insulating layer 205 may beappropriately selected, so that the insulating layer 205 has a highreflectivity of about 95% or more with respect to the first peakwavelength (λ1) of the first light generated by the active layer 220.

The first light generated by the active layer 220 may be reflectedinward by the insulating layer 205, the reflection layer 280, and theoptical filter layer 260 having reflection characteristics, and beincident on the optical wavelength conversion layer 250, thus increasingthe optical wavelength conversion efficiency of the optical wavelengthconversion layer 250. The first light having the first peak wavelength,which is generated by the active layer 220, may be converted into thesecond light having the second peak wavelength by the optical wavelengthconversion layer 250, and the second light may be emitted to the outsidethrough the optical filter layer 260. Therefore, the LED 200 may emit ahigh-purity color light.

FIG. 7 is a cross-sectional view of a part of an LED 300 according toanother exemplary embodiment of the inventive concept.

Referring to FIG. 7, the LED 300 may include a light-emitting structure340, an optical wavelength conversion layer 350, and an optical filterlayer 360. The light-emitting structure 340 may include asecond-conductivity-type semiconductor layer 330, an active layer 320,and a first-conductivity-type semiconductor layer 310, which aresequentially disposed on a conductive substrate 303. The light-emittingstructure 340, the optical wavelength conversion layer 350, and theoptical filter layer 360 of the LED 300 illustrated in FIG. 7respectively correspond to the light-emitting structure 140, the opticalwavelength conversion layer 150, and the optical filter layer 160 of theLED 100 illustrated in FIG. 1, and redundant descriptions thereof willbe omitted. The stacking order of the light-emitting structure 340illustrated in FIG. 7 is substantially identical to the stacking orderof the light-emitting structure 140 illustrated in FIG. 4. That is, thefirst-conductivity-type semiconductor layer 310 may be disposed on theactive layer 320, and the active layer 320 may be disposed on thesecond-conductivity-type semiconductor layer 330. According to anotherexemplary embodiment, the first-conductivity-type semiconductor layer310 may have an uneven upper surface.

The LED 300 may further include a transparent substrate 370 on theoptical filter layer 360, and a reflection layer 380 that may cover aside of the optical wavelength conversion layer 350 and/or a side of thelight-emitting structure 340. The transparent substrate 370 and thereflection layer 380 respectively correspond to the transparentsubstrate 170 a of the LED 100 b illustrated in FIG. 2 and thereflection layer 180 of the LED 100 d illustrated in FIG. 5, andredundant descriptions thereof will be omitted. According to anotherexemplary embodiment, the LED 200 may include a transparent layerbetween the optical wavelength conversion layer 250 and the opticalfilter layer 260, instead of the transparent substrate 270.

The LED 300 may be configured as illustrated in FIG. 7 to achieve highpower and increase current dispersion efficiency and heat dissipationefficiency.

A first electrode 301 may be electrically connected to thefirst-conductivity-type semiconductor layer 310 and may be electricallyisolated from the second-conductivity-type semiconductor layer 330 andthe active layer 320. The first electrode 301 may be electricallyconnected to the first-conductivity-type semiconductor layer 310 via oneor more contact holes CH. The contact hole CH may pass through thesecond electrode 302, the second-conductivity-type semiconductor layer330, and the active layer 320 and extend to the inside of thefirst-conductivity-type semiconductor layer 310. The contact hole CH maybe formed using an etching process, for example, inductively coupledplasma-reactive ion etching (ICP-RIE).

An insulating layer 305 may be disposed on the first electrode 301 so asto electrically isolate the first electrode 301 from the secondelectrode 302, the second-conductivity-type semiconductor layer 330, andthe active layer 320. The insulating layer 305 may be disposed betweenthe first electrode 301 and the second electrode 302 and may also bedisposed on an inner sidewall of the contact hole CH. The insulatinglayer 305 may include an insulating material such as SiO₂, SiO_(x)N_(y),or Si_(x)N_(y).

The contact hole CH may expose a contact region C of thefirst-conductivity-type semiconductor layer 310, and a portion of thefirst electrode 301 may contact the contact region C of thefirst-conductivity-type semiconductor layer 310 through the contact holeCH.

In order to reduce the contact resistance between the first electrode301 and the first-conductivity-type semiconductor layer 310, the number,shape, and pitch of the contact holes CH or the exposed area of thefirst-conductivity-type semiconductor layer 310 may be appropriatelyselected. The contact holes CH may be arranged in rows and columns invarious forms to improve the current flow. The number and size of thecontact holes CH may be appropriately adjusted so that the area of thecontact region C becomes about 0.1% to about 20% of the planar area ofthe light-emitting structure 340. For example, the area of the contactregion C may be about 0.5% to about 15%, or about 1% to about 10% of theplanar area of the light-emitting structure 340. When the area of thecontact region C is less than about 0.1% of the planar area of thelight-emitting structure 340, the current dispersion is not uniform,thus degrading the light-emitting characteristics. When the area of thecontact region C is about 20% or more of the planar area of thelight-emitting structure 340, the light-emitting area of thelight-emitting structure 340 is relatively reduced, thus degrading thelight-emitting characteristics and reducing the brightness of the LED300.

A diameter of the contact region C of the first-conductivity-typesemiconductor layer 310 may be in the range of about 1 μm to about 50μm, and the number of the contact holes CH may be 1 to 48,000 accordingto the entire planar area of the light-emitting structure 340. Thenumber of the contact holes CH may be 2 to 45,000, 5 to 40,000, or 10 to35,000. The distance between the contact holes CH may be in the range ofabout 10 μm to about 1,000 μm, about 50 μm to about 700 μm, about 100 μmto about 500 μm, or 150 μm to about 400 μm. The contact holes CH may bearranged in a matrix form with rows and columns.

When the distance between the contact holes CH is less than 10 μm, thenumber of the contact holes CH increases and the light-emitting area ofthe light-emitting structure 340 relatively decreases, thus reducing thelight-emitting efficiency. When the distance between the contact holesCH is greater than 1,000 μm, the current diffusion becomes difficult,thus reducing the light-emitting efficiency. The depth of the contactholes CH may be different depending on the thicknesses of the secondelectrode 302, the second-conductivity-type semiconductor layer 330, andthe active layer 320 and may be in the range of about 0.1 μm to about5.0 μm. The second electrode 302 may be disposed under thesecond-conductivity-type semiconductor layer 330 and be electricallyconnected to the second-conductivity-type semiconductor layer 330. Thesecond electrode 302 may have a pad-forming region E that extendsoutward from the light-emitting structure 340 and is exposed externally.An electrode pad 304 may be disposed on the pad-forming region E so asto connect the external terminal to the second electrode 302. Althoughonly one pad-forming region E is illustrated, a plurality of electrodeforming regions E may be formed if necessary. The pad-forming region Emay be disposed at one edge of the light-emitting structure 340 toincrease the light-emitting area.

An etching stopper 306 may be disposed around the electrode pad 304. Theetching stopper 306 may include an insulating material and may be formedin the pad-forming region E after the formation of the light-emittingstructure 340 and before the formation of the second electrode 302. Theetching stopper 306 may serve as an etching stopper during an etchingprocess for the pad-forming region E.

The first electrode 301 may include a material that forms an ohmiccontact with the first-conductivity-type semiconductor layer 310 and hasa high reflectivity. The first electrode 301 may include a material suchas Li, Ca, LiF/Ca, LiF/Al, Al, Ag, Mg, or Au.

FIG. 8 is a cross-sectional view of a part of an LED 400 according toanother exemplary embodiment of the inventive concept.

Referring to FIG. 8, the LED 400 may include a substrate 406, and afirst-conductivity-type semiconductor layer 410, an active layer 420,and a second-conductivity-type semiconductor layer 430, which aresequentially arranged on the substrate 406. A buffer layer 407 may bedisposed between the substrate 406 and the first-conductivity-typesemiconductor layer 410.

The substrate 406 may be an insulating substrate such as a sapphiresubstrate. However, the substrate 406 is not limited thereto, and thesubstrate 406 may be a conductive substrate or a semiconductorsubstrate. For example, the substrate 406 may include SiC, Si, MgAl₂O₄,MgO, LiAlO₂, LiGaO₂, or GaN.

The buffer layer 407 may include In_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1).For example, the buffer layer 407 may include GaN, MN, AlGaN, or InGaN.The buffer layer 407 may have a multilayer structure formed by combininga plurality of layers or may include a layer having a composition thatgradually changes.

The first-conductivity-type semiconductor layer 410, the active layer420, and the second-conductivity-type semiconductor layer 430 of the LED400 illustrated in FIG. 8 may respectively correspond to thefirst-conductivity-type semiconductor layer 110, the active layer 120,and the second-conductivity-type semiconductor layer 130 of the LED 100illustrated in FIG. 1, and redundant descriptions thereof will beomitted. The active layer 120 in the exemplary embodiment of FIG. 1 isstacked on the entire surface of the first-conductivity-typesemiconductor layer 110, but the active layer 420 in the exemplaryembodiment of FIG. 8 is disposed on a portion of thefirst-conductivity-type semiconductor layer 410.

The LED 400 may further include a first electrode 401 disposed onanother portion of the first-conductivity-type semiconductor layer 410,and an ohmic contact layer 402 b and a second electrode 402 asequentially disposed on the second-conductivity-type semiconductorlayer 430.

The first electrode 401 may include a material such as Ag, Ni, Al, Cr,Rh, Pd, Ir, Ru, Mg, Zn, Pt, or Au, but is not limited thereto. The firstelectrode 401 may have a single layer structure or a multilayerstructure having two or more layers. The LED 400 may further include apad electrode layer on the first electrode 401. The pad electrode layermay be a metal layer including at least one of Au, Ni, or Sn.

The ohmic contact layer 402 b may be transparent and conductive so thatthe light generated by the active layer 420 is emitted upward. The ohmiccontact layer 402 b may be a metal layer, such as Ag, Au, or Al, atransparent conductive oxide layer, or a nitride layer. For example, theohmic contact layer 402 b may include at least one of indium tin oxide(ITO), zinc-doped indium tin oxide (ZITO), zinc indium oxide (ZIO),gallium indium oxide (GIO), zinc tin oxide (ZTO), fluorine-doped tinoxide (FTO), aluminium-doped zinc oxide (AZO), gallium-doped zinc oxide(GZO), In₄Sn₃O₁₂, or zinc magnesium oxide (Zn_((1-x))Mg_(x)O) (0≦x≦1).

The second electrode 402 a may include at least one of Al, Au, Cr, Ni,Ti, or Sn. The second electrode 402 a may be electrically connected toan external device (e.g., a lead frame, a package substrate and so on.)via a bonding wire W.

The LED 400 may further include an optical wavelength conversion layer450 on the ohmic contact layer 402 b and on the second electrode 402 a.The LED 400 may also include an optical filter layer 460 on the opticalwavelength conversion layer 450.

The optical wavelength conversion layer 450 may be configured to absorbfirst light having a first peak wavelength, which is emitted from theactive layer 402, and emit second light having a second peak wavelength.The first light may pass through the ohmic contact layer 402 b and thesecond electrode 402 a and be incident on the optical wavelengthconversion layer 450. The bonding wire W bonded to the second electrode402 a may pass through the optical wavelength conversion layer 450. Thatis, a portion of the bonding wire W may pass through the opticalwavelength conversion layer 450. The optical wavelength conversion layer450 of FIG. 8 corresponds to the optical wavelength conversion layer 150of FIG. 1, and a detailed description thereof will be omitted.

The optical filter layer 460 may reflect the first light having thefirst peak wavelength which is emitted from the active layer 420, andtransmit the second light having the second peak wavelength which isemitted from the optical wavelength conversion layer 450. The opticalfilter layer 460 corresponds to the optical filter layer 160 of FIG. 1,and a detailed description thereof will be omitted.

The LED 400 may further include a transparent substrate 470 on theoptical filter layer 460, and a reflection layer 480 that covers a sideof the active layer 420. The transparent substrate 470 may function as asupport substrate for forming the optical filter layer 460. Thereflection layer 480 may substantially prevent the light generated bythe active layer 420 from leaking toward the side surface thereof andimprove the light-emitting efficiency of the second light having thesecond peak wavelength. As illustrated in FIG. 8, the reflection layer480 may cover the sides of the first-conductivity-type semiconductorlayer 410, the active layer 420, and the second-conductivity-typesemiconductor layer 430 and may also extend to the sides of thesubstrate 406 and the buffer layer 407. The transparent substrate 470and the reflection layer 480 respectively correspond to the transparentsubstrate 170 a of the LED 100 b illustrated in FIG. 2 and thereflection layer 180 of the LED 100 d illustrated in FIG. 5, anddetailed descriptions thereof will be omitted.

FIG. 9 is a cross-sectional view of a part of an LED 500 according toanother exemplary embodiment of the inventive concept.

Referring to FIG. 9, the LED 500 may include a substrate 501, and afirst-conductivity-type semiconductor layer 504, an active layer 505,and a second-conductivity-type semiconductor layer 506, which aresequentially arranged on the substrate 501. A buffer layer 502 may bedisposed between the substrate 501 and the first-conductivity-typesemiconductor layer 504. The first-conductivity-type semiconductor layer504, the active layer 505, and the second-conductivity-typesemiconductor layer 506 of the LED 500 illustrated in FIG. 9 maycorrespond to respective ones of the first-conductivity-typesemiconductor layer 110, the active layer 120, and thesecond-conductivity-type semiconductor layer 130 of the LED 100illustrated in FIG. 1, and redundant descriptions thereof will beomitted.

The substrate 501 may be an insulating substrate such as a sapphiresubstrate. However, the substrate 501 is not limited thereto, and thesubstrate 501 may be a conductive substrate or a semiconductorsubstrate. For example, the substrate 501 may include SiC, Si, MgAl₂O₄,MgO, LiAlO₂, LiGaO₂, or GaN.

The buffer layer 502 may include In_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1).For example, the buffer layer 502 may include GaN, MN, AlGaN, or InGaN.The buffer layer 502 may have a thickness of about 0.1 nm to about 500nm. The buffer layer 502 may include ZrB₂, HfB₂, ZrN, HfN, or TiN. Thebuffer layer 502 may include a plurality of layers or may include alayer whose composition gradually changes.

The first-conductivity-type semiconductor layer 504 and thesecond-conductivity-type semiconductor layer 506 may have a single-layerstructure. In some embodiments, if necessary, thefirst-conductivity-type semiconductor layer 504 and thesecond-conductivity-type semiconductor layer 506 may have multilayerstructures with different compositions or thicknesses. For example, atleast one of the first-conductivity-type semiconductor layer 504 and thesecond-conductivity-type semiconductor layer 506 may include a carrierinjection layer capable of improving electron and/or hole injectionefficiency and may have various superlattice structures.

The LED 500 may further include a V-pit forming layer 520 on thefirst-conductivity-type semiconductor layer 504. The V-pit forming layer520 may be adjacent to the first-conductivity-type semiconductor layer504. The V-pit forming layer 520 may have a V-pit density of about 1×10⁸cm⁻² to about 5×10⁹ cm⁻². According to some exemplary embodiments, theV-pit forming layer 520 may have a thickness of about 200 nm to about800 nm Δn inlet of a V-pit 521 may have a width D of about 200 nm toabout 800 nm Because the vertical cross-section of the V-pit 521 has aV-like shape, the V-pit 521 is generally referred to as a V-pit. TheV-pit 521 formed in the V-pit forming layer 520 may have an apex angle(θ) of about 10 degrees to about 90 degrees, for example, about 20degrees to about 80 degrees.

According to the present exemplary embodiment, the V-pit 521 may have agrowth plane ((0001) plane) substantially parallel to a substrate plane,and a growth plane ((1-101) plane, (11-22) plane, or other inclinedcrystal plane) inclined with respect to the substrate plane at the sametime. The V-pit 521 may be formed around a penetration potential passingthrough the light-emitting structure and prevent a current fromconcentrating around the penetration potential.

The V-pit forming layer 520 may include GaN or doped GaN.

A position at which the V-pit 521 is formed in the V-pit forming layer520 may be adjusted by a growth temperature. That is, when the growthtemperature is relatively low, the formation of the V-pit 521 may startat a lower position. On the contrary, when the growth temperature isrelatively high, the formation of the V-pit 521 may start at a higherposition.

Assuming that the V-pit forming layer 520 has substantially the sameheight, an upper width of the V-pit 521 may further increase if theformation of the V-pit 521 is started at a lower position.

The LED 500 may further include a film quality enhancement layer 530 onthe V-pit 520. The film quality enhancement layer 530 may have acomposition of M_(x)Ga_(1-x)N. Herein, M may be Al or In, and x may be0.01≦x≦0.3. In some exemplary embodiments, x may be 0.02≦x≦0.08. If thevalue of x is excessively small, the film quality enhancement effect maybe insufficient. On the contrary, if the value of x is excessivelylarge, the light-emitting characteristics may be deteriorated. In thefilm quality enhancement layer 530, the value of x may be constant.Alternatively, the film quality enhancement layer 530 may have amultilayer structure in which a GaN layer and an M_(x)Ga_(1-x)N layer(where M is Al or In and 0.01≦x≦0.3) are alternately stacked.Alternatively, the film quality enhancement layer 530 may be asuperlattice layer in which a GaN layer and an M_(x)Ga_(1-x)N layer(where M is Al or In and 0.01≦x≦0.3) are alternately stacked. The filmquality enhancement layer 530 may have a thickness of about 20 nm toabout 100 nm.

The film quality enhancement layer 530 may be substantially entirelyformed along an upper surface 523 of the V-pit forming layer 520. Inaddition, the film quality enhancement layer 530 may have asubstantially constant thickness in a direction perpendicular to theupper surface 523 of the V-pit generating layer 520.

The film quality enhancement layer 530 may fill at least a portion ofthe V-pit 521 by covering the inside of the V-pit 521 of the V-pitforming layer 520 to a predetermined thickness. A V-pit 531 of the filmquality enhancement layer 530 may be recessed into the V-pit 521 of theV-pit forming layer 520. The thickness of the film quality enhancementlayer 530 in a direction perpendicular to the upper surface 523 of theV-pit forming layer 520 may be about 5% to about 20% of the thickness ofthe V-pit forming layer 520.

Dimensions of the V-pit 531 formed in the film quality enhancement layer530 may be substantially equal or similar to dimensions of the V-pit 521of the V-pit forming layer 520.

An upper surface 533 of the film quality enhancement layer 530 may havean improved surface roughness as compared with an upper surface 523 ofthe V-pit forming layer 520. For example, the surface roughness of theupper surface 533 of the film quality enhancement layer 530 may be about60% or less of the surface roughness of the upper surface 123 of theV-pit forming layer 520. The surface roughness may be measured using anatomic force microscope (AFM). The surface roughness may be based on ameasurement on the upper surface except for the V-pits 521 and 531. Thesurface roughness may be determined by measuring a uniformity (flatness)of an interface. For example, the uniformity of the film qualityenhancement layer 530 and an interface adjacent thereto may be superiorto the uniformity of the V-pit forming layer 520 and an interfaceadjacent thereto.

By improving the surface roughness of the upper surface 533 of the filmquality enhancement layer 530, the surface roughness of a barrier layerand a quantum well layer in the active layer 505 disposed thereon can beimproved. As a result, a non-luminous recombination between electronsand holes may be reduced, thus remarkably improving the light-emittingcharacteristics.

The LED 500 may further include a superlattice layer 540 overlying thefilm quality enhancement layer 530. The superlattice layer 540 may havea structure in which a plurality of In_(x)Al_(y)Ga_((1-x-y))N layers(0≦x<1, 0≦y<1, 0≦x+y<1) having different compositions or differentimpurity content are repeatedly stacked, or may include an insulatingmaterial layer in part. The superlattice layer 540 may cause uniformlight emission to occur in a wide area by accelerating the diffusion ofa current.

In the superlattice layer 540, a V-pit 541 may be formed correspondingto the V-pit 531 formed in the film quality enhancement layer 530.

The superlattice layer 540 may fill at least a portion of the V-pit 531by covering the inside of the V-pit 531 of the V-pit forming layer 530to a predetermined thickness. A V-pit 541 of the superlattice layer 540may be recessed into the V-pit 531 of the film quality enhancement layer530.

The second-conductivity-type semiconductor layer 506 may further includean electron blocking layer (EBL) at a position adjacent to the activelayer 505. Another V-pit 551 is formed into the active layer 505overlapping with the V-pit 541. The EBL may have a structure in which aplurality of In_(x)Al_(y)Ga_((1-x-y))N layers having differentcompositions are stacked, or may have a single-layer or multilayerstructure including Al_(y)Ga_((1-y))N. Since a band gap of the EBL isgreater than a band gap of the active layer 505, the EBL is capable ofpreventing electrons from crossing the second-conductivity-typesemiconductor layer 506.

As the V-pit 521 formed in the V-pit forming layer 520 becomes closer tothe thickness direction of each layer, i.e., thesecond-conductivity-type semiconductor layer 506, the V-shaped valleymay become gentle and may become substantially flat due to thesuperlattice layer 540 or the second-conductivity-type semiconductorlayer 506.

The LED 500 may further include a first electrode 519 a disposed on aportion of the first-conductivity-type semiconductor layer 504, and anohmic contact layer 518 and a second electrode 519 b sequentiallydisposed on the second-conductivity-type semiconductor layer 506.

The first electrode 519 a is not limited thereto. The first electrode519 a may include a material such as Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn,Pt, Au and may have a single-layer structure or a multilayer structurehaving two or more layers. The LED 400 may further include a padelectrode layer on the first electrode 519 a. The pad electrode layermay include at least one of Au, Ni, or Sn.

The ohmic contact layer 518 may be transparent and conductive so thatthe light generated by the active layer 505 is emitted upward. The ohmiccontact layer 518 may be a metal layer, such as Ag, Au, and Al, atransparent conductive oxide layer, or a nitride layer. For example, theohmic contact layer 518 may include at least one of indium tin oxide(ITO), zinc-doped indium tin oxide (ZITO), zinc indium oxide (ZIO),gallium indium oxide (GIO), zinc tin oxide (ZTO), fluorine-doped tinoxide (FTO), aluminium-doped zinc oxide (AZO), gallium-doped zinc oxide(GZO), In₄Sn₃O₁₂, or zinc magnesium oxide (Zn_((1-x))Mg_(x)O) (0≦x≦1).

The second electrode 519 b may include at least one of Al, Au, Cr, Ni,Ti, or Sn. The second electrode 519 b may be electrically connected toan external device (e.g., a lead frame, a package substrate, etc.) via abonding wire W.

The LED 500 may further include an optical wavelength conversion layer550 on the ohmic contact layer 518 and the second electrode 519 b, andan optical filter layer 560 on the optical wavelength conversion layer550.

The optical wavelength conversion layer 550 may be disposed on the ohmiccontact layer 518 and the second electrode 519 b and may be configuredto absorb the first light having the first peak wavelength, which isemitted from the active layer 505, and emit the second light having thesecond peak wavelength. The first light may pass through the ohmiccontact layer 518 and the second electrode 519 b and be incident on theoptical wavelength conversion layer 550. The bonding wire W bonded tothe second electrode 419 b may be disposed to pass through the opticalwavelength conversion layer 550. That is, a portion of the bonding wireW may pass through the optical wavelength conversion layer 550. Theoptical wavelength conversion layer 550 corresponds to the opticalwavelength conversion layer 150 of FIG. 1, and a detailed descriptionthereof will be omitted.

The optical filter layer 560 may reflect the first light having thefirst peak wavelength which is emitted from the active layer 505, andtransmit the second light having the second peak wavelength which isemitted from the optical wavelength conversion layer 550. The opticalfilter layer 560 corresponds to the optical filter layer 160 of FIG. 1,and a detailed description thereof will be omitted.

The LED 500 may further include a transparent substrate 570 on theoptical filter layer 560, and a reflection layer 580 that covers a sideof at least the active layer 505. The transparent substrate 170 a mayfunction as a support substrate for forming the optical filter layer560. The reflection layer 580 may be provided to prevent the lightgenerated by at least the active layer 505 from leaking toward the sidesurface thereof and improve the light-emitting efficiency of the secondlight having the second peak wavelength. As illustrated in FIG. 9, thereflection layer 580 may cover the sides of the first-conductivity-typesemiconductor layer 504, the V-pit forming layer 520, the film qualityenhancement layer 530, the superlattice layer 540, the active layer 505,and the second-conductivity-type semiconductor layer 506 and may extendto the sides of the substrate 501 and the buffer layer 502. Thetransparent substrate 570 and the reflection layer 580 respectivelycorrespond to the transparent substrate 170 a of the LED 100 billustrated in FIG. 2 and the reflection layer 180 of the LED 100 dillustrated in FIG. 5, and redundant descriptions thereof will not berepeated.

FIG. 10 is a cross-sectional view of an LED package 600 according toanother exemplary embodiment of the inventive concept.

Referring to FIG. 10, the LED package 600 may include the LED 400, apart of which is illustrated in FIG. 8. Since the LED 400 has beendescribed above with reference to FIG. 8, a redundant descriptionthereof will be omitted.

The LED package 600 may further include a package substrate 610 and anencapsulation body 603. The LED 400 may be mounted on the packagesubstrate 610 and be electrically connected to the package substrate 610via the bonding wire W.

The package substrate 610 may include a substrate body 611, an upperelectrode 613, a lower electrode 614, and a through-electrode 612 thatconnects the upper electrode 613 to the lower electrode 614. A body ofthe package substrate 610 may include a resin, a ceramic, or a metal,and the upper or lower electrode 613 or 614 may be a metal layerincluding Au, Cu, Ag, or Al. For example, the package substrate 610 maybe a printed circuit board (PCB), a metal core PCB (MCPCB), ametal-based PCB (MPCB), or a flexible PCB (FPCB), and the configurationof the package substrate 610 may be employed in various forms.

The encapsulation body 603 may have a dome-shaped lens structure with aconvex upper surface. However, according to some embodiments, anorientation angle of a light emitted through the upper surface of theencapsulation body 603 can be adjusted by forming a lens structure witha convex or concave surface.

FIG. 11 is a cross-sectional view of an LED package 700 according toanother exemplary embodiment of the inventive concept.

Referring to FIG. 11, the LED package 700 may include an LED 400′ thatis substantially the same as the LED 400 of FIG. 8 from which theoptical wavelength conversion layer, the optical filter layer, and thetransparent substrate are removed. The description of the LED 400illustrated in FIG. 8 will substitute for the description of the LED400′. The LED 400′ may emit first light having a first peak wavelength.The first peak wavelength may be included in a wavelength band of bluevisible light or a wavelength band of ultraviolet light. For example,the LED 400′ may be a blue LED. The LED package 700 may further includea package body 702 and a pair of lead frames 703 a and 703 b.

The LED 400′ may be mounted on the lead frames 703 a and 703 b, andelectrodes may be electrically connected to the lead frames 703 a and703 b through wires W. According to another exemplary embodiment, theLED 400′ may be mounted on a region other than the lead frames 703 a and703 b, for example, the package body 702.

The package body 702 may have a cup-shaped groove so as to improve thelight reflection efficiency of the LED package 700. The package body 702may be a resin including a high-reflectivity powder. Thehigh-reflectivity powder included in the package body 702 may preventthe first light emitted by the LED 400′ from being absorbed into thepackage body 702 or leaking toward the side of the LED package 700, thusincreasing the light brightness of the LED package 700. Thehigh-reflectivity powder may include a metal powder having highreflectivity, for example, an Al or Ag powder. The high-reflectivitymetal powder may be appropriately included in the range in which thepackage body 702 is maintained as an insulating material. In addition,the high-reflectivity powder may include a ceramic powder, for example,at least one of TiO₂, Al₂O₃, Nb₂O₅, Al₂O₃, or ZnO.

The package body 702 may be a curing resin or a semi-curing resin. Thecuring resin may be flowable before curing and may be curable when heatenergy or ultraviolet energy is applied thereto. The semi-curing stateis a state that is not completely cured, but may mean a state in whichcuring is sufficiently progressed to have handleability orprocessability. The semi-cured resin may be pressed at an appropriatetemperature and attached to the surface of the LED 400′.

According to some exemplary embodiments, the package body 702 may bemade of the same material and may be one body. That is, the package body702 may be formed by molding the same material.

The package body 702 may have electrically insulating properties. Forexample, the package body 702 may include a silicon resin, an epoxyresin, or any mixtures thereof.

The LED package 700 may further include an optical wavelength conversionlayer 750 that contacts an inner sidewall of the package body 702 andcontacts the upper surface of the LED 400′ in a space defined by thepackage body 702.

The optical wavelength conversion layer 750 may encapsulate the LED 400′and the wire W. The optical wavelength conversion layer 750 may absorbfirst light having a first peak wavelength, which is emitted from theLED 400′, and emit second light having a second peak wavelength. Thesecond peak wavelength may be different from the first peak wavelengthand may be included in a wavelength band of a second color of visiblelight which is different from a first color. The second color may be oneof a red color, a green color, and a yellow color.

Various materials, such as phosphors and/or quantum dots, may be used asa wavelength conversion material for converting the wavelength of thefirst light emitted from the LED 400′.

The phosphors used for the optical wavelength conversion layer 750 mayhave the following empirical formulas and colors.

Oxide-based: yellow color and green color Y₃Al₅O₁₂:Ce, Tb₃Al₅O₁₂:Ce,Lu₃Al₅O₁₂:Ce

Silicate-based: yellow color and green color (Ba,Sr)₂SiO₄:Eu, yellowcolor and orange color (Ba,Sr)₃SiO₅:Ce

Nitride-based: green color β-SiAlON:Eu, yellow color La₃Si₆O₁₁:Ce,orange color α-SiAlON:Eu, red color CaAlSiN₃:Eu, Sr₂Si₅N₈:Eu,SrSiAl₄N₇:Eu, SrLiAl₃N₄:Eu,Ln_(4-x)(Eu_(z)M_(1-z))_(x)Si_(12-y)Al_(y)O_(3+x+y)N_(18-x-y) (0.5≦x≦3,0<z<0.3, 0<y≦4)

Herein, Ln may be at least one of group Ma elements or rare-earthelements, and M may be at least one of calcium (Ca), barium (Ba),strontium (Sr), and magnesium (Mg).

Fluoride-based: KSF-based red color K₂SiF₆:Mn₄ ⁺, K₂TiF₆:Mn₄ ⁺,NaYF₄:Mn₄ ⁺, NaGdF₄:Mn₄ ⁺, K₃SiF₇:Mn₄ ⁺

The composition of the phosphor needs to basically conform withstoichiometry, and the respective elements may be substituted by otherelements included in the respective groups of the periodic table. Forexample, strontium (Sr) may be substituted by at least one of barium(Ba), calcium (Ca), or magnesium (Mg) of alkaline-earth group II, and Ymay be substituted by at least one of terbium (Tb), lutetium (Lu),scandium (Sc), or gadolinium (Gd). In addition, europium (Eu), which isan activator, may be substituted by at least one of cerium (Ce), terbium(Tb), praseodymium (Pr), erbium (Er), or ytterbium (Yb) according to adesired energy level. The activator may be applied solely or a subactivator may be additionally applied for the modification of phosphorcharacteristics.

The wavelength conversion layer 750 may include a quantum dot (QD) asthe wavelength conversion material, instead of the phosphor or incombination with the phosphor.

The LED package 700 may further include an optical filter layer 760 onthe optical wavelength conversion layer 750. The optical filter layer760 may extend to cover the upper surface of the package body 720.

The optical filter layer 760 may reflect the first light having thefirst peak wavelength which is emitted from the LED 400′, and transmitthe second light having the second peak wavelength emitted from theoptical wavelength conversion layer 750.

The optical filter layer 760 may have a multilayer reflection structurein which a plurality of dielectric films having different refractiveindexes are alternately stacked. For example, the optical filter layer760 may have a multilayer reflection structure in which a firstdielectric film having a first refractive index (n1) and a firstthickness (d1) and a second dielectric film having a second refractiveindex (n2) and a second thickness (d2) are alternately and repeatedlystacked. According to an exemplary embodiment, the optical filter layer160 may be a DBR configured to reflect the first light having the firstpeak wavelength which is emitted from the LED 400′.

The multilayer reflection structure may be formed by repeatedly stackinga plurality of dielectric films having different refractive indexestwice or more. Each of the first and second dielectric films in themultilayer reflection structure may include oxide or nitride (e.g.,SiO₂, SiN, SiO_(x)N_(y), TiO₂, Nb₂O₅, Si₃N₄, Al₂O₃, TiN, MN, ZrO₂,TiAlN, TiSiN, etc.), or any mixtures thereof. For example, the firstdielectric film may include silicon oxide (SiO₂), and the seconddielectric film may include titanium oxide (TiO₂) or niobium oxide(Nb₂O₅).

A refractive index of each of the first and second dielectric films maybe determined within the range of about 1.4 to about 3.0. When the firstpeak wavelength of the first light emitted by the LED 400′ is λ1, thethicknesses of the first and second dielectric films are λ1/4n1 andλ2/4n2, respectively.

FIG. 12 is a cross-sectional view of an LED package 900 according toanother exemplary embodiment of the inventive concept.

Referring to FIG. 12, the LED package 900 may include a light-emittingstructure S, an optical wavelength conversion layer 950, and an opticalfilter layer 960. The light-emitting structure S may include afirst-conductivity-type semiconductor layer 904, an active layer 905,and a second-conductivity-type semiconductor layer 906, which aresequentially stacked. The light-emitting structure S, the opticalwavelength conversion layer 950, and the optical filter layer 960 of theLED package 900 illustrated in FIG. 12 may respectively correspond tothe light-emitting structure 140, the optical wavelength conversionlayer 150, and the optical filter layer 160 of the LED 100 illustratedin FIG. 1, and redundant descriptions thereof will be omitted. Thestacking order of the light-emitting structure S illustrated in FIG. 12is substantially identical to the stacking order of the light-emittingstructure 140 illustrated in FIG. 4. That is, thefirst-conductivity-type semiconductor layer 904 may be disposed on theactive layer 905, and the active layer 905 may be disposed on thesecond-conductivity-type semiconductor layer 906. In addition, thefirst-conductivity-type semiconductor layer 904 may have an uneven uppersurface so as to improve the light extraction efficiency of the LEDpackage 900 and the single-crystal quality of the light-emittingstructure S.

The LED package 900 may further include a transparent substrate 970 onthe optical filter layer 960, and a reflection layer 980 that covers aside of the optical wavelength conversion layer 950. The reflectionlayer 980 may cover a side of a lateral encapsulation 927. Thereflection layer 980 may cover the sides of the optical filter layer 960and the transparent substrate 970 depending on the manufacturingprocess. The transparent substrate 970 and the reflection layer 980respectively correspond to the transparent substrate 170 a of the LED100 b illustrated in FIG. 2 and the reflection layer 180 of the LED 100d illustrated in FIG. 5, and redundant descriptions thereof will beomitted. According to another exemplary embodiment, the LED package 900may include a transparent layer between the optical wavelengthconversion layer 950 and the optical filter layer 960, instead of thetransparent substrate 970.

The LED package 900 may further include a first electrode electricallyconnected to the first-conductivity-type semiconductor layer 904, and asecond electrode electrically connected to the second-conductivity-typesemiconductor layer 906.

The second electrode may include a second electrode unit 909 includingan ohmic contact unit 909 a disposed under the second-conductivity-typesemiconductor layer 906 and directly electrically connected to thesecond-conductivity-type semiconductor layer 906, and an electrode unit909 b connected to the ohmic contact unit 909 a. The second electrodemay further include a second pad 919 connected to the second electrodeunit 909, and a second metal post 929 connected to the second pad 919and functioning as an external terminal.

The first electrode may be electrically connected to thefirst-conductivity-type semiconductor layer 904 via a contact holepassing through the second electrode unit 909, thesecond-conductivity-type semiconductor layer 906, and the active layer905. The first electrode may include a first electrode unit 908 directlyelectrically connected to the first-conductivity-type semiconductorlayer 904, a first pad 918 electrically connected to the first electrodeunit 908, and a first metal post 928 connected to the first pad 918 andfunctioning as an external terminal.

The LED package 900 may further include an insulating layer 907 thatprovides electrical insulation between the first electrode connected tothe first-conductivity-type semiconductor layer 904 and the secondelectrode connected to the second-conductivity-type semiconductor layer906. The insulating layer 907 may include a reflection structure forreflecting first light generated by the active layer 905.

The LED package 900 may further include a lateral encapsulation 927 thatsupports the light-emitting structure S and the first and secondelectrodes, protects the light-emitting structure S and the first andsecond electrodes from the outside, and provides electrical insulationbetween the first metal post 928 and the second metal post 929.

The first light generated by the active layer 905 may be reflectedinward by the insulating layer 907, the reflection layer 980, and theoptical filter layer 960 having reflection characteristics, and beincident on the optical wavelength conversion layer 950, thus increasingthe optical wavelength conversion efficiency of the optical wavelengthconversion layer 950. The first light having the first peak wavelength,which is generated by the active layer 905, may be converted into secondlight having a second peak wavelength by the optical wavelengthconversion layer 950, and the second light may be emitted to the outsidethrough the optical filter layer 960. Therefore, the LED package 900 mayemit a high-purity color light.

FIGS. 13A to 13K are cross-sectional views for describing a method ofmanufacturing the LED package 900 of FIG. 12, according to an exemplaryembodiment of the inventive concept.

Referring to FIG. 13A, a light-emitting structure S may be formed on asubstrate 901 at a wafer level. The light-emitting structure S may beprovided by sequentially forming a first-conductivity-type semiconductorlayer 904, an active layer 905, and a second-conductivity-typesemiconductor layer 906. The substrate 901 may be an insulatingsubstrate such as a sapphire substrate. However, the substrate 901 isnot limited thereto and may include SiC, Si, MgAl₂O₄, MgO, LiAlO₂,LiGaO₂, or GaN.

Referring to FIG. 13B, after a mesa etching process is performed toexpose a portion E1 of the first-conductivity-type semiconductor layer904, a first insulating layer 907 a may be deposited on thelight-emitting structure S. Due to the mesa etching process, one or moremesas may be formed in each LED package.

Referring to FIG. 13C, after a portion of the first insulating layer 907a is etched, a conductive ohmic material may be deposited on theresulting structure to form first and second electrode units 908 and909. A second insulating layer 907 b may be formed on the firstinsulating layer 907 a and the first and second electrode units 908 and909, which may be partially exposed by an etching process. Each of thefirst and second electrode units 908 and 909 may be a reflectiveelectrode including one selected from the group consisting of Ag, Al,Ni, Cr, Cu, Au, Pd, Pt, Sn, W, Rh, Ir, Ru, Mg, Zn, and alloys thereof.The second electrode unit 909 may include an ohmic contact unit 909 aand an electrode unit 909 b.

Referring to FIG. 13D, first and second pads 918 and 919 may be formedon the first and second electrode units 908 and 909, respectively. Thefirst and second pads 918 and 919 may be electrically connected to thefirst and second electrode units 908 and 909, respectively.

Referring to FIG. 13E, an isolation process may be performed to separatethe substrate 901 into individual chips. The isolation process may beperformed by a blade, for example. Any other suitable process may beused as long as the process is capable of cutting the light-emittingstructure S while the substrate 901 is not cut. Through the isolationprocess, the light-emitting structure S may be separated into individualchips and be mounted on the substrate 901. The light-emitting structureS obtained by the isolation process may have a trapezoidal shape inwhich an upper side is shorter than a lower side. This may form aninclined surface at a side of the light-emitting structure S.

A third insulating layer 907 c may be formed on the inclined surface ofthe light-emitting structure S, the first and second pads 918 and 919,and the second insulating layer 907 b, and the first and second pads 918and 919 may be partially exposed. The third insulating layer 907 c mayprovide passivation together with the remaining first and secondinsulating layers 907 a and 907 b formed in the previous process.

Referring to FIG. 13F, first and second metal posts 928 and 929 may beformed on the first and second pads 918 and 919, respectively. Each ofthe first and second metal posts 928 and 929 may include copper (Cu),for example. Each of the first and second metal posts 928 and 929 mayinclude a conductive material.

Referring to FIG. 13G, a lateral encapsulation 927 may be formed to filla gap between the first and second metal posts 928 and 929 and fill agap between the first and second metal posts 928 and 929 of the adjacentlight-emitting structures S.

When the lateral encapsulation 927 is formed, a material of the lateralencapsulation 927 may have high Young's modulus so as to obtain highstiffness and may have a high thermal conductivity so as to dischargeheat from the light-emitting structure S. In addition, a lightreflective material may be included in the lateral encapsulation 927 soas to reflect a light downward. The light reflective material mayinclude TiO₂ or Al₂O₃, for example.

The lateral encapsulation 927 may be formed by coating an encapsulationmaterial until upper portions of the first and second metal posts 928and 929 are covered, and by exposing end portions of the first andsecond metal posts 928 and 929 using a planarization process such asgrinding.

As shown in FIG. 13H, the substrate 901 may then be removed. Thisprocess may include a process of temporarily bonding a support substrate931 to surfaces on which the first and second metal posts 928 and 929are present. A bonding material 932 such as an ultraviolet curablematerial may be used. Then, the substrate 901 may be removed by aprocess such as grinding or laser lift-off. If necessary, a texturingprocess may be further performed on a portion of thesecond-conductivity-type semiconductor layer 906 to increase the lightextraction efficiency of the LED package. Uneven patterns P may beformed on the upper surface of the second-conductivity-typesemiconductor layer 906.

Referring to FIG. 13I, an optical wavelength conversion layer 937 may beformed on the light-emitting structure S. Various optical wavelengthconversion materials, such as phosphors and/or quantum dots, may be usedfor the optical wavelength conversion layer 937.

Referring to FIG. 13J, a process of cutting the light-emitting structureS for each individual package may be performed. In some embodiments, thecutting process may be performed by removing the support substrate 931,attaching an adhesive tape 941, and separating the light-emittingstructure S into individual packages, for example, by blade cutting.

As shown in FIG. 12, a reflection layer 980 may be formed on the side ofthe optical wavelength conversion layer 937. The reflection layer 980may cover only the side of the optical wavelength conversion layer 937.The reflection layer 980 may also cover the side of the lateralencapsulation 927.

On the other hand, aside from the above processes, FIG. 13K, an opticalfilter layer 960 may be formed on a transparent substrate 970. Theoptical filter layer 960 may reflect first light having a first peakwavelength which is emitted from the light-emitting structure S, andtransmit second light having a second peak wavelength which is emittedfrom the optical wavelength conversion layer 937.

The transparent substrate 970 with the optical filter layer 960 formedthereon may be turned over and bonded to the optical wavelengthconversion layer 937 as illustrated in FIG. 12. After the opticalwavelength conversion layer 937 is semi-cured to have adhesiveproperties, the transparent substrate 970 may be pressed so that theoptical filter layer 960 contacts the upper surface of the opticalwavelength conversion layer 937. Then, the optical wavelength conversionlayer 937 is cured. In this manner, the transparent substrate 970 withthe optical filter layer 960 may be bonded to the optical wavelengthconversion layer 937. Alternatively, the transparent substrate 970 withthe optical filter layer 960 may be bonded to the optical wavelengthconversion layer 937 by using an adhesive or an adhesive film. In someother embodiments, the transparent substrate 970 with the optical filterlayer may be directly bonded to the optical wavelength conversion layer937 without turning over the transparent substrate 970. That is, thetransparent substrate 970 may directly contact the upper surface of theoptical wavelength conversion layer 937.

As described above, in some embodiments, the transparent substrate 970with the optical filter layer 960 may be cut into individual packageshaving the same size and bonded to the optical wavelength conversionlayer 937. In some embodiments, the transparent substrate 970 with theoptical filter layer 960 may be bonded to substantially the entiresurface of the structure illustrated in FIG. 13I. Then, the resultingstructure is cut into individual packages. The reflection layer 980 maybe formed on the side of the cut individual packages.

The chip scale package obtained through the above-described processeshas substantially the same package size as a semiconductorlight-emitting device (i.e., LED chip). As a result, a large amount oflight per unit area can be achieved. In addition, since all processesare performed at the wafer level, the inventive concept is suitable formass production. Furthermore, the wavelength conversion material such asphosphors may be integrally prepared with the LED chip.

FIG. 14 is a block diagram of a three-color light-emitting apparatus1000 using LED packages LED1, LED2, and LED3 according to variousexemplary embodiments of the inventive concept.

Referring to FIG. 14, the three-color light-emitting apparatus 1000 mayinclude first, second, and third LED packages LED1, LED2, and LED3.

The first and second LED packages LED1 and LED2 may include any one ofthe LED packages or structures illustrated in FIGS. 1 to 12. The thirdLED package LED3 may not include an optical wavelength conversion layerand an optical filter layer. For example, the third LED package LED3 maybe a modification of any one of the LED packages illustrated in FIGS. 1to 12, from which the optical wavelength conversion layer and theoptical filter layer are removed.

The first, second, and third LED packages LED1, LED2, and LED3 may havesubstantially the same light-emitting structure. For example, theconfigurations and material compositions of the light-emittingstructures of the first, second, and third LED packages LED1, LED2, andLED3 may be substantially identical to one another. Each of thelight-emitting structures of the first, second, and third LED packagesLED1, LED2, and LED3 may emit first light having a first peak wavelengthwithin a wavelength band of blue visible light. The light-emittingstructure of the first LED package LED1 will be referred to as a firstlight-emitting structure, the light-emitting structure of the second LEDpackage LED2 will be referred to as a second light-emitting structure,and the light-emitting structure of the third LED package LED3 will bereferred to as a third light-emitting structure.

The first LED package LED1 may further include a first opticalwavelength conversion layer and a first optical filter layer as comparedwith the third LED package LED3.

The first optical wavelength conversion layer may be disposed on thefirst light-emitting structure and be configured to absorb first lighthaving a first peak wavelength, which is emitted from the firstlight-emitting structure, and emit second light having a second peakwavelength different from the first peak wavelength. The second peakwavelength may be included in a wavelength band of green visible light.

The first optical filter layer may be disposed on the first opticalwavelength conversion layer and be configured to reflect the first lighthaving the first peak wavelength which is emitted from the firstlight-emitting structure. The first optical filter layer may transmitthe second light having the second peak wavelength which is emitted fromthe first optical wavelength conversion layer.

The second LED package LED2 may further include a second opticalwavelength conversion layer and a second optical filter layer ascompared with the third LED package LED3.

The second optical wavelength conversion layer may be disposed on thesecond light-emitting structure and be configured to absorb the firstlight having the first peak wavelength which is emitted from the secondlight-emitting structure, and emit a third light having a third peakwavelength different from the first peak wavelength and the second peakwavelength. The third peak wavelength may be included in a wavelengthband of red visible light.

The second optical filter layer may be disposed on the second opticalwavelength conversion layer and be configured to reflect the first lighthaving the first peak wavelength which is emitted from the secondlight-emitting structure. The second optical filter layer may transmitthe third light having the third peak wavelength which is emitted fromthe second optical wavelength conversion layer.

For example, the first LED package LED1 may output green light, thesecond LED package LED2 may output red light, and third LED package LED3may output blue light.

Each of the first and second optical filter layers may have a structurein which a first dielectric film with a first refractive index and asecond dielectric film with a second refractive index are alternatelystacked. The first dielectric film and the second dielectric filmprovided in the first optical filter layer may have substantially thesame dielectric constant and thickness as the first dielectric film andthe second dielectric film provided in the second optical filter layer.According to another exemplary embodiment, the first dielectric film andthe second dielectric film provided in the first optical filter layermay have a different dielectric constant and/or thickness from the firstdielectric film and the second dielectric film provided in the secondoptical filter layer, so that the first optical filter layer transmitsthe second light having the second peak wavelength and the secondoptical filter layer transmits the third light having the third peakwavelength.

A planar area of the third light-emitting structure may be smaller thana planar area of the first light-emitting structure or the secondlight-emitting structure. Also, the planar area of the secondlight-emitting structure may be smaller than the planar area of thefirst light-emitting structure. In some embodiments, the planar area ofthe first light-emitting structure may be larger than the planar area ofthe first light-emitting structure or the second light-emittingstructure. The first and second optical wavelength conversion layers andthe first and second optical filter layers may be respectively disposedon the first and second light-emitting structures. Therefore, thelight-emitting efficiency of the first and second LED packages LED1 andLED2 may be reduced by the wavelength conversion and the opticalfiltering, as compared with the third LED package LED3 that directlyemit light without wavelength conversion or optical filtering. In orderto compensate for the reduced light-emitting efficiency, the first andsecond LED packages LED1 and LED2 may have a larger planar area than thethird LED package LED3.

According to the present exemplary embodiment, the first to third LEDpackages LED1 to LED3 of the three-color light-emitting apparatus 1000may have the same light-emitting structure. Therefore, the first tothird LED packages LED1 to LED3 may use the same driving power, and thethree-color light-emitting apparatus 1000 may be driven even when onlyone type of power is supplied as the driving power of the three-colorlight-emitting apparatus 1000.

If the types of the light-emitting structures provided in the first,second and third LED packages LED1 to LED3 are different from oneanother to emit different color light, the driving powers thereof mayneed to be different from one another. In order to drive the three-colorlight-emitting apparatus including these first to third LED packagesLED1 to LED3, it may be necessary to supply three different types ofpowers or to supply one type of power and additionally generate secondand third powers through voltage division or the like. Thus, theefficiency of power may be degraded and the circuit may becomecomplicated. With the present exemplary embodiment, however, since thefirst, second, and third LED packages LED1 to LED3 that emit differentcolor light have the same light-emitting structure, the first, secondand third LED packages LED1 to LED3 may be driven using one type ofpower and the power circuit may be simply configured. In addition, thepower efficiency may not be reduced. Furthermore, it is possible toprevent color deviation by increasing the planar areas of the first andsecond LED packages LED1 and LED2 so as to solve the reduction in thelight-emitting efficiency of the first and second LED packages LED 1 andLED2.

In addition, with the present exemplary embodiment, the light of thefirst color is not included in the light emitted by the first and secondLED packages LED1 and LED2. Therefore, the first and second LED packagesLED1 and LED2 are capable of emitting high-purity light of second andthird colors. Therefore, the three-color light-emitting apparatus 100 iscapable of expressing a wide range of colors.

FIG. 16 is a block diagram of a display device 1100 using LED packagesaccording to various exemplary embodiments of the inventive concept.FIG. 17A is a block diagram of a pixel in the display device 1100 ofFIG. 16.

Referring to FIGS. 16 and 17, the display device 1100 may include aplurality of pixels P. The pixels P may be arranged in rows and columns.The pixels P may be implemented by using the three-color light-emittingapparatus 1000 of FIG. 14 or may have a similar structure thereto.

The pixel P may include at least two subpixels SP. For example, if thesubpixels SP are arranged in a Bayer pattern, a first pixel P mayinclude red and green subpixels SP, a second pixel P may include blueand green subpixels SP, and the first pixel P and the second pixel P maybe repeatedly arranged. The pixel P may include red, green, and bluesubpixels SP. The pixel P may include red, green, blue, and whitesubpixels SP.

The pixel is illustrated in FIG. 17A as including first, second, andthird subpixels SP1, SP2, and SP3, but the inventive concept is notlimited thereto. For example, the pixel P can include four or moresubpixels with different combinations of subpixels including red, green,blue and white subpixels SP. The first subpixel SP1 may include a firstLED, the second subpixel SP2 may include a second LED, and the thirdsubpixel SP3 may include a third LED.

The first LED may include a first light-emitting structure, a firstoptical wavelength conversion layer, and a first optical filter layer.The first light-emitting structure may include a first-conductivity-typesemiconductor layer, an active layer, and a second-conductivity-typesemiconductor layer and emit first light having a first peak wavelength.The first optical wavelength conversion layer may be disposed on thefirst light-emitting structure to absorb the first light having thefirst peak wavelength emitted from the first light-emitting structure,and emit second light having a second peak wavelength different from thefirst peak wavelength. The first optical filter layer may be disposed onthe first optical wavelength conversion layer to reflect the first lightemitted from the first light-emitting structure and transmit the secondlight emitted from the first optical wavelength conversion layer.

The second LED may include a second light-emitting structure, a secondoptical wavelength conversion layer, and a second optical filter layer.The second light-emitting structure may have substantially the sameconfiguration and material composition as the first light-emittingstructure, may include the first-conductivity-type semiconductor layer,the active layer, and the second-conductivity-type semiconductor layer,and emit first light having a first peak wavelength. The second opticalwavelength conversion layer may be disposed on the second light-emittingstructure to absorb the first light having the first peak wavelengthemitted from the second light-emitting structure, and emit a third lighthaving a third peak wavelength different from the first and second peakwavelengths. The second optical filter layer may be disposed on thesecond optical wavelength conversion layer to reflect the first lightemitted from the second light-emitting structure and transmit the thirdlight emitted from the second optical wavelength conversion layer.

The third LED may have a third light-emitting structure that includesthe first-conductivity-type semiconductor layer, the active layer, andthe second-conductivity-type semiconductor layer and emits the firstlight having the first peak wavelength.

The first, second, and third light-emitting structures of the first,second, and third subpixels SP1, SP2, and SP3 may have substantially thesame configuration in size and material composition. For example, thefirst, second, and third light-emitting structures may be driven byusing the same driving power and emit first light of the same color. Acolor of the first light may be a blue color. That is, the first peakwavelength may be included in a wavelength band of blue visible light.The second peak wavelength may be included in a wavelength band of asecond color, for example, a wavelength band of green visible light. Thethird peak wavelength may be included in a wavelength band of a thirdcolor, for example, a wavelength band of red visible light.

As illustrated in FIG. 17A, the first LED of the first subpixel SP1 mayemit green light, the second LED of the second subpixel SP2 may emit redlight, and the third LED of the third subpixel SP3 may emit blue light.

Unlike the first and second subpixels SP1 and SP2, the third subpixelSP3 may not include the optical wavelength conversion layer and theoptical filter layer. Therefore, the third subpixel SP3 may have higherlight-emitting efficiency than the first and second subpixels SP1 andSP2. In order for the first, second, and third subpixels SP1, SP2, andSP3 to have the same maximum brightness, the planar areas of the firstand second subpixels SP1 and SP2 may be larger than the planar area ofthe third subpixel SP3. In other words, in some embodiments, the planararea of the third subpixel SP3 among the first to third subpixels SP1,SP2, and SP3 may be smallest.

However, since the first, second and third subpixels SP1, SP2, and SP3include the light-emitting structure having substantially the sameconfiguration in size and material composition, the first, second andthird subpixels SP1, SP2, and SP3 may be driven by the same drivingpower. Therefore, the first, second, and third subpixels SP1, SP2, andSP3 may have the same driving circuit configuration. An example of adriving circuit of the subpixel P is illustrated in FIG. 18. The firstto third subpixels SP1, SP2, and SP3 will be collectively referred to asa subpixel SP.

In some other embodiments, the planar areas of the subpixels SP1, SP2,and SP3 may be substantially the same. For example, as shown in FIG.17B, first, second, and third subpixels SP1, SP2 and SP3 may each havesubstantially the same planar area. Similar to the pixel P of FIG. 17A,in the pixel P′ of FIG. 17B, a first LED of the first subpixel SP1′ mayemit green light, a second LED of the second subpixel SP2′ may emit redlight, and a third LED of the third subpixel SP3′ may emit blue light.The first LED may include a first light-emitting structure. The secondLED may include a second light-emitting structure. The third LED mayinclude a third light-emitting structure.

As a result, in some embodiments, the resulting pixel P′ shown in FIG.17B may comprise two or more first subpixel SP1′ each having a firstlight-emitting structure, two or more second subpixels SP2 each having asecond light-emitting structure, a single third subpixel SP3 having athird light-emitting structure. The first, second, and thirdlight-emitting structures each include a first-conductivity-typesemiconductor layer, an active layer, and a second-conductivity-typesemiconductor layer and configured to emit first light having a firstpeak wavelength as in the above-described embodiments.

Also, other elements may be similarly formed as in the above-describedembodiments. For example, a first optical wavelength conversion layer(not illustrated) may be disposed on the first light-emitting structureand configured to absorb the first light emitted from the firstlight-emitting structure and emit second light having a second peakwavelength different from the first peak wavelength. Also, a secondoptical wavelength conversion layer (not illustrated) may be disposed onthe second light-emitting structure and configured to absorb the firstlight emitted from the second light-emitting structure and emit a thirdlight having a third peak wavelength different from the first and secondpeak wavelength. Further, first and second optical filter layers (notillustrated) may be respectively disposed on the first and secondoptical wavelength conversion layers.

In some embodiments, an optical wavelength conversion layer may not beformed on the third light-emitting structure. Also, an optical filterlayer may not be formed on the optical wavelength conversion layeroverlying the third light-emitting structure.

In some embodiments, each of the first, second and third light-emittingstructures have substantially the same planar area.

As in the pixel of FIG. 17A, the first LED of the first subpixel SP1 mayemit green light. The second LED of the second subpixel SP2 may emit redlight and the third LED of the third subpixel SP3 may emit blue light.

FIG. 18 is a circuit diagram of the subpixel SP illustrated in FIG. 17A.

Referring to FIG. 18, the subpixel SP may include a switching transistorTRs, a driving transistor TRd, and a storage capacitor Cst. The drivingtransistor TRd may generate a driving current between a first drivingpower VDD and a second driving power VSS and output the generateddriving current to an LED. The LED may include one of the first to thirdlight-emitting structures. As described above, since the first to thirdlight-emitting structures are driven by the same driving power, thepixel circuit and the voltage level of the driving power do not changeaccording to the type of the subpixel SP.

The switching transistor TRs may be connected to a gate line GL throughwhich a scan signal is transmitted and a data line DL through which adata signal is transmitted. The switching transistor TRs may store thedata signal in the storage capacitor Cst in response to the scan signal.The storage capacitor Cst may temporarily store the data signaltransferred from the switching transistor TRs and constantly maintain agate-source voltage of the driving transistor TRd during one frame. Thedriving transistor TRd may adjust an amount of a current flowing fromthe first driving power VDD to the second driving power VSS through theLED in response to the data signal transferred from the switchingtransistor TRs. Accordingly, the LED may emit light at a brightnesscorresponding to the data signal.

As illustrated in FIG. 18, since the subpixel SP is driven by the samedriving power, regardless of the color to be displayed, the pixelcircuit and the power circuit can be simplified. In addition, since eachsubpixel SP emits high-purity color light, the display device 1100according to the present exemplary embodiment may display a wide rangeof colors.

It will be understood that when an element, such as a layer, a region,or a substrate, is referred to as being “on,” “connected to” or “coupledto” another element, it may be directly on, connected or coupled to theother element or intervening elements may be present. In contrast, whenan element is referred to as being “directly on,” “directly connectedto” or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like reference numerals refer tolike elements throughout. As used herein, the term “and/or” includes anyand all combinations of one or more of the associated listed items.Expressions such as “at least one of”, when preceding a list ofelements, modify the entire list of elements and do not modify theindividual elements of the list.

Also, though terms “first” and “second” are used to describe variousmembers, components, regions, layers, and/or portions in variousembodiments of the inventive concept, the members, components, regions,layers, and/or portions are not limited to these terms. These terms areused only to differentiate one member, component, region, layer, orportion from another one. Therefore, a member, a component, a region, alayer, or a portion referred to as a first member, a first component, afirst region, a first layer, or a first portion in an embodiment may bereferred to as a second member, a second component, a second region, asecond layer, or a second portion in another embodiment.

Spatially relative terms, such as “above”, “upper”, “beneath”, “below”,“lower”, and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “above” may encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the inventiveconcept. As used herein, the singular forms “a”, “an”, and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be understood that terms such as“comprise”, “include”, and “have”, when used herein, specify thepresence of stated features, integers, steps, operations, elements,components, or combinations thereof, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, or combinations thereof.

While the inventive concept has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the following claims.

What is claimed is:
 1. A multi-color light-emitting apparatuscomprising: a single substrate; first, second, and third light-emittingstructures formed on the single substrate, the first, second, and thirdlight-emitting structures each including a first-conductivity-typesemiconductor layer, an active layer, and a second-conductivity-typesemiconductor layer and configured to emit first light having a firstpeak wavelength; a first optical wavelength conversion layer disposed onthe first light-emitting structure and configured to absorb the firstlight emitted from the first light-emitting structure and emit secondlight having a second peak wavelength different from the first peakwavelength; a second optical wavelength conversion layer disposed on thesecond light-emitting structure and configured to absorb the first lightemitted from the second light-emitting structure and emit a third lighthaving a third peak wavelength different from the first and second peakwavelengths; first and second optical filter layers respectivelydisposed on the first and second optical wavelength conversion layersand configured to reflect the first light emitted from the first andsecond light-emitting structures.
 2. The multi-color light-emittingapparatus of claim 1, wherein configurations of the first to thirdlight-emitting structures are substantially identical to one another. 3.The multi-color light-emitting apparatus of claim 1, wherein a planararea of the third light-emitting structure is smaller than a planar areaof the first light-emitting structure or the second light-emittingstructure.
 4. The multi-color light-emitting apparatus of claim 1,wherein the first peak wavelength is included in a wavelength band ofblue visible light, the second peak wavelength is included in awavelength band of red visible light, and the third peak wavelength isincluded in a wavelength band of green or yellow visible light.
 5. Themulti-color light-emitting apparatus of claim 1, wherein a dielectricconstant of at least a portion of the second optical filter layer isdifferent from a dielectric constant of least a portion of the firstoptical filter layer.
 6. The multi-color light-emitting apparatus ofclaim 1, wherein a thickness of the second optical filter layer isdifferent from a thickness of the first optical filter layer.
 7. Adisplay device comprising: a plurality of pixels each comprising atleast a first subpixel with a first LED, and a second subpixel with asecond LED, wherein the first LED includes: a first light-emittingstructure; a first optical wavelength conversion layer disposed on thefirst light-emitting structure and configured to absorb a first lightemitted from the first light-emitting structure and emit second lighthaving a second peak wavelength different from the first peakwavelength; a first optical filter layer disposed on the first opticalwavelength conversion layer and configured to reflect the first lightemitted from the first light-emitting structure and transmit the secondlight emitted from the first optical wavelength conversion layer,wherein the second LED includes: a second light-emitting structureincluding the first-conductivity-type semiconductor layer, the activelayer, and the second-conductivity-type semiconductor layer andconfigured to emit the first light having the first peak wavelength; asecond optical wavelength conversion layer disposed on the secondlight-emitting structure and configured to absorb the first lightemitted from the second light-emitting structure and emit a third lighthaving a third peak wavelength different from the first and second peakwavelengths; and a second optical filter layer disposed on the secondoptical wavelength conversion layer and configured to reflect the firstlight emitted from the second light-emitting structure and transmit thethird light emitted from the second optical wavelength conversion layer,wherein each of the pixels further comprises a third subpixel with athird LED, wherein the third LED includes: a third light-emittingstructure including the first-conductivity-type semiconductor layer, theactive layer, and the second-conductivity-type semiconductor layer andconfigured to emit the first light having the first peak wavelength,wherein the first LED emits red light, the second LED emits green light,and the third LED emits blue light.
 8. The display device of claim 7,wherein a planar area of the third subpixel among the first, second, andthird subpixels is smallest.
 9. The display device of claim 7, whereinthe first, second, and third subpixels are configured to be driven bythe same driving power.